About buy2rent.io: method, sources and limitations
buy2rent.io is a rental investment analysis tool for Spain. You paste a listing (Idealista, Fotocasa, Habitaclia, pisos.com, yaencontre); it estimates the market rent, calculates gross and net yield, tax and cash flow, and gives an investment score.
Who we are
- buy2rent.io is an independent project based in Madrid. It does not sell property, earns no agency commission and is not affiliated with any property portal.
- Contact: support@buy2rent.io.
What the tool does
- Reads the listing (text, link or screenshots): price, size, rooms, floor, lift, condition, energy certificate.
- Monthly rent computed by code: the published sub-area price (capped at the district average in Madrid and Barcelona, where these averages include many short-term lets), otherwise the district average, corrected for size (small flats rent for more per m²), then a low / median / high range with its precision level. Accuracy figures: see the limits below.
- Calculates gross and net yield, community fees, IBI, tax (EU/EEA non-resident, non-EU or resident) and cash flow with a mortgage, with a month-by-month breakdown. Costs included: half a month of vacancy a year, community fees, IBI, insurance (250 €/year), maintenance (5% of rent) and, by default for non-residents, a letting agency (8% of rent, can be switched off). The tax shown is for year 1: it rises afterwards as deductible interest falls; the tool also gives the year-10 estimate.
- Gives an investment score from 1 to 10 with strengths, weaknesses and a verdict.
Data sources
- Rents by neighbourhood: Idealista monthly asking-price reports, updated every quarter. Coverage: Madrid, Barcelona, Valencia, Málaga and the Costa del Sol (79 neighbourhoods and towns).
- Official data loaded automatically: IRAV and CPI (INE), rental housing price index IPVA (INE), Euribor (Bank of Spain).
- Neighbourhood socio-demographics: household income (INE income distribution atlas) and regional unemployment (INE, EPA).
- Buying costs: 2026 ITP and AJD rates for all 17 regions, official notary and land registry scales.
How the analysis is produced
- An AI model (Claude, by Anthropic) reads the listing and writes the analysis from the data above.
- Automatic server-side checks verify the result: the computed rent range is enforced (the AI may only move the median rent by 10% for a property feature), weaknesses that contradict the listing are removed, and missing data is never presented as a flaw of the property.
Limitations
- Reference rents are asking rents from listings, not signed rents: negotiation often lowers them by a few percent. Tested on 444 rentals, the estimate is typically 14% away from the asking rent, which falls inside the range about 6 times out of 10 and below it about 2 times out of 10. The “cautious case” (low end) is therefore not a floor. The test mostly covers Madrid; it is weaker for Barcelona, Valencia and Málaga.
- Results are indicative estimates, not financial or tax advice.
- Outside the covered cities, the tool applies conservative assumptions.
Pricing
- 2 free analyses, no card required.
- 24-hour pass: €9. 7-day pass: €19. Monthly subscription: €49.
- The calculators (rent increase, buying costs, yield, mortgage) and the neighbourhood rent pages are free.
Updated : 2026-11-03
How to assess a Spanish listing’s rental yield: spreadsheet, agent or buy2rent.io →