# Airbnb or invest — the short-let calculator

> A browser calculator at https://vibes.obel.dev/airbnb-or-invest/ that models running a property as a short let (Airbnb, Booking.com) against putting the same money into a unit trust, money market fund or government securities. It reports the return each earns, which is ahead after a chosen number of years, and the occupancy at which they tie. It covers buying a place, buying land and building, and a place you already own. Every input is encoded in the URL query string, so a link opens with the whole scenario already filled in.

This file is the complete parameter reference for building a link to this
calculator. The tables are generated from the calculator's own field
definitions — if this file and the app disagree, the app is right and this is a
bug.

There are two pages for this calculator, and they take exactly the same
parameters:

- https://vibes.obel.dev/airbnb-or-invest/
  The default. One question at a time, in plain language. Each explains what the
  input is, why it moves the answer, and what it typically runs to in developed
  and in developing markets, and any of them can be skipped.
- https://vibes.obel.dev/airbnb-or-invest/advanced/
  Every input on one screen, for someone who already knows what they mean.

Everything after the `?` is identical, so build the query string once and put
either base in front of it. Use the default unless the person you are helping
has asked for the dense one.

## How to build a link

1. Start from `https://vibes.obel.dev/airbnb-or-invest/`.
2. Append `?` then `&`-joined `name=value` pairs from the tables below.
3. **Only include parameters you are changing.** Anything you leave out falls
   back to its default — provided the link carries at least one parameter this
   file documents. A link carrying none is not a defaults link; see rule 4.
4. A link carrying at least one parameter the calculator recognises — `m`, `c`,
   or any name from the tables below — is self-contained. Opening it resets
   every parameter you left out back to its default, ignores whatever scenario
   the visitor had saved, and does not overwrite it. A URL with nothing
   recognisable in it does the opposite. A bare `https://vibes.obel.dev/airbnb-or-invest/`,
   or one carrying only unrecognised parameters such as `utm_source=x`,
   restores whatever scenario that visitor last had — so a bare link is not a
   link to the defaults. To send the default scenario, pass one parameter
   explicitly, such as the mode at its own default, `m=buy`.
5. Values are plain decimal numbers — no thousands separators, no currency
   symbol, no `%`. Negatives are fine where the range allows.
6. **All money is Kenyan shillings (KES), always.** The `c` parameter changes
   the display currency only. It does not convert the numbers you pass and it
   does not change the model, so convert to KES yourself before building the
   link.
7. Out-of-range values are never rejected, only clamped — a link stays valid
   while quietly meaning something else. Money is clamped to 0 to 1000000000000;
   everything else to the range in its table.
8. The on-screen sliders move in fixed steps, but **URL values do not have to
   be multiples of those steps.** Pass the real figure.
9. Percentages are whole-number percents: `50` means 50%, not 0.5.
10. Output the finished URL as raw text on its own line. Do not wrap it in a
    markdown link, do not percent-encode it, and do not write `&` as `&`.
11. These parameter names are specific to this calculator. Do not reuse them on
    another vibes calculator — several short names mean different things there.

## Modes

`m` chooses where you're starting from. Default `buy`. Case-sensitive, and any value other than `build` or `own` or `keep` is treated as `buy`.

| value | shown as | means |
| --- | --- | --- |
| `buy` | Buying a place | Buy a finished flat or house and furnish it. The money at stake is `pr` plus `bfee` plus `furn`. |
| `build` | Buying land and building | Buy a plot and build, then furnish. Nothing is earned during the `bm` build months. The money at stake is `land`, `bc` with `fee` and `cont`, plus `furn`. |
| `own` | I own it — or I could sell | You own the place already. The alternative is selling it today, less `sp`, and investing that plus the furnishing money. Uses `val`. |
| `keep` | I own it and I'm keeping it | You own the place and would keep it either way, so only `furn` is at stake. Its value, growth, fixed costs and sale are the same on both paths and left out. |

`pr` and `bfee` apply only under `buy`; `land`, `bc`, `fee`, `cont`, `bm` and `wv` only under `build`; `val` only under `own`. `fix`, `app`, `sp` and `cgt` are ignored under `keep`. Setting a parameter the mode doesn't use does nothing.

## Display currency

`c` sets the currency results are *displayed* in. Default `KES`. Accepted values: `KES`, `UGX`, `USD`, `GBP`, `EUR`, `ZAR`, `NGN`, `INR`, `AED`. An unrecognised code is ignored entirely. Display only — see rule 6.

## Parameters

### Buying it — mode `buy` only

| param | means | default | range | notes |
| --- | --- | --- | --- | --- |
| `pr` | Purchase price | 9000000 | KES | What the flat or house costs, before any fees. |
| `bfee` | Stamp duty, legal & valuation | 5 | 0 to 15 % | Transfer costs on top of the price, as a share of it. None of it comes back when you sell. |

### Building it — mode `build` only

| param | means | default | range | notes |
| --- | --- | --- | --- | --- |
| `land` | Plot price | 3000000 | KES | Paid on day one. Set to 0 if the plot is already yours. |
| `bc` | Build cost | 6000000 | KES | Shell, finishes and services — construction only. Fees and contingency go on top. |
| `fee` | Design, approvals & supervision | 8 | 0 to 25 % | Architect, engineer and local-authority approvals. A share of build cost. |
| `cont` | Contingency | 10 | 0 to 30 % | Spare money for overruns, which are the norm. A share of build cost plus fees. |
| `bm` | Months to build | 12 | 1 to 48 months | No guests while it goes up. The build cost is drawn evenly over these months. |
| `wv` | Finished place is worth | 110 | 50 to 200 % | A share of everything it cost, land included. Above 100 means you built for less than buyers would pay. |

### The place you own — mode `own` only

| param | means | default | range | notes |
| --- | --- | --- | --- | --- |
| `val` | What it would sell for today | 9000000 | KES | Selling it and investing the proceeds is the alternative, so this is the money the Airbnb keeps tied up. |

### Getting it guest-ready

| param | means | default | range | notes |
| --- | --- | --- | --- | --- |
| `furn` | Furnishing & setup | 800000 | KES | Furniture, appliances, linen, kitchenware, a smart lock, photos. Paid once the place is ready. |
| `ref` | Replacing worn furnishings | 15 | 0 to 50 % | Per year, as a share of the setup cost. Guests wear things out far faster than a tenant would. |
| `ramp` | Months to get fully booked | 4 | 0 to 24 months | A new listing has no reviews. Bookings climb from nothing to your figure over these months. |

### What it earns

| param | means | default | range | notes |
| --- | --- | --- | --- | --- |
| `rate` | Nightly rate | 6000 | KES | What a guest pays per night, before the platform's cut. |
| `occ` | Nights booked | 55 | 0 to 100 % | Share of the year with a guest in, once the listing is established. 55% is about 200 nights. |
| `stay` | Average stay | 3 | 1 to 30 nights | Nights per booking. Every checkout means a clean and fresh linen. |
| `rg` | Nightly rate growth | 5 | -5 to 20 % | Per year. |

### Cost of running it

| param | means | default | range | notes |
| --- | --- | --- | --- | --- |
| `plat` | Platform fee | 3 | 0 to 20 % | What Airbnb or Booking.com keeps from each booking. |
| `mgmt` | Co-host or manager | 15 | 0 to 35 % | A share of bookings, if someone else runs it for you. 0 if you do it yourself. |
| `cln` | Cleaning & laundry per stay | 1200 | KES | Per checkout, including soap, toilet paper and coffee. |
| `util` | Utilities & internet | 12000 | KES | Per month, booked or not: power, water, Wi-Fi, TV, security, service charge. |
| `rep` | Repairs & upkeep | 60000 | KES | Per year. Short lets wear a place faster than long ones. |
| `itax` | Tax on bookings | 10 | 0 to 40 % | A share of everything you collect, before costs come off. |

### Holding the property — modes `buy`, `build`, `own` only

| param | means | default | range | notes |
| --- | --- | --- | --- | --- |
| `fix` | Rates, insurance & ground rent | 40000 | KES | Per year. What it costs to own the place at all, whether or not anyone stays. |
| `app` | Property value growth | 4 | -5 to 20 % | Per year. |

### Getting out — modes `buy`, `build`, `own` only

| param | means | default | range | notes |
| --- | --- | --- | --- | --- |
| `sp` | Selling costs | 3 | 0 to 15 % | Agent and legal fees when you sell — at the end, and under "I own it" if you sold today instead. |
| `cgt` | Capital gains tax | 15 | 0 to 40 % | Charged on what you sell for above what the place cost you. Only the gain is taxed. |

### The alternative

| param | means | default | range | notes |
| --- | --- | --- | --- | --- |
| `inv` | Return if invested instead | 12 | 0 to 30 % | Per year, compounding. A unit trust, money market fund, T-bills or a government bond. |
| `itx` | Tax on those returns | 15 | 0 to 40 % | Withholding tax taken off interest before you're paid. |
| `ife` | Annual management fee | 1 | 0 to 5 % | Charged on the balance every year. Unit trusts charge one; T-bills bought directly don't. |

### Time & inflation

| param | means | default | range | notes |
| --- | --- | --- | --- | --- |
| `h` | Years to compare over | 10 | 1 to 30 years | The whole comparison is measured at this year, with the place sold. |
| `infl` | Inflation | 6 | 0 to 20 % | Per year. Pushes up cleaning, utilities, repairs and the fixed costs. |

## Worked examples

Buying a KES 12M two-bed at KES 9,000 a night, booked 60% of the year:
https://vibes.obel.dev/airbnb-or-invest/?pr=12000000&rate=9000&occ=60

Building on a plot you already own: KES 8M to build over 14 months:
https://vibes.obel.dev/airbnb-or-invest/?m=build&land=0&bc=8000000&bm=14

A flat you own and could sell for KES 12.2M (about UGX 350M), managed yourself, shown in shillings of Uganda:
https://vibes.obel.dev/airbnb-or-invest/?m=own&val=12200000&mgmt=0&c=UGX

Keeping a flat you own either way — is KES 1M of furnishing worth it at KES 5,000 a night?:
https://vibes.obel.dev/airbnb-or-invest/?m=keep&furn=1000000&rate=5000

## What the calculator does with these

`m` sets what is at stake. Under `buy` it is the price plus `bfee` plus `furn`; under
`build`, the plot plus `bc` with `fee` and `cont`, plus `furn`; under `own`, what a sale
today would bring (`val` less `sp`) plus `furn`; under `keep`, only `furn`. The market
path is handed that whole amount on day one and compounds at `inv`, net of `itx` and
`ife`.

On the Airbnb path, a build draws `bc` evenly over `bm` months earning nothing, while
whatever hasn't been drawn keeps compounding at the market rate. Once the place is
ready, bookings climb from nothing to `occ` over `ramp` months. Each month earns
`occ` of the nights at `rate` (growing at `rg`), less `plat`, `mgmt` and `itax` as
shares of bookings, `cln` per stay of `stay` nights, `util`, `rep`, and `ref` of the
furnishing cost — all but the shares inflating at `infl`. `fix` is paid from day one.
What it makes is reinvested at the market rate, and a loss is charged at it.

At the end the property is sold: its value (the price, `val`, or the build's cost
times `wv`) grown at `app`, less `sp` and `cgt` on the gain over what it cost.
Furnishings are worth nothing. Under `keep` the property is held on both paths, so
its value, growth, fixed costs and sale cancel and are left out.

The page reports which path wins, the crossover year, the Airbnb's IRR against the
market's net rate, the occupancy at which the two tie, and which single input would
flip the verdict.

The defaults sit between Nairobi and Kampala, but nothing is hardcoded to either.
Every tax, rate and cost is a plain input.

Not modelled: mortgages or construction loans — this compares cash against cash.
Nor are seasonality (`occ` is a year-round average), minimum-stay rules, licensing and
tourism levies, building rules that ban short lets, or the owner's own time. It is a
model, not advice.

## Related

- https://vibes.obel.dev/llms.txt — index of the other tools
- https://vibes.obel.dev/build-or-invest/llms.txt — a whole block let by the month rather than one unit by the night
- https://vibes.obel.dev/rent-or-buy/llms.txt — buy a home to live in or let, with a mortgage