Rental payback can look attractive, but the tax and regulatory treatment is not settled for detached auxiliary dwellings. Any calculator on this site is illustrative only and not tax advice.
Start with gross rent, then subtract realistic annual costs before thinking about tax: insurance differences, repairs, maintenance, utilities, cleaning between long-term tenancies, compliance checks, financing, and possible property-related charges.
If future law allows a specific relief, the calculation may change. If it does not, taxable rental income and other obligations may materially change the payback period.
We deliberately do not model short-stay platform income as the default path. Current Rent-a-Room guidance excludes short-term guests and online booking style leisure stays.