Methodology
How BytScore compares homes and checks investments
BytScore uses visible deterministic rules for two different decisions: comparing homes against one buyer profile and checking rental investments. It explains the assumptions and what to verify next; it is not a professional valuation or advice.
Mortgage and operating costs
The mortgage payment is a financing cost, calculated from the loan, rate and term; zero interest means equal principal payments. Operating owner costs exclude the mortgage. They include entered fees, maintenance and other included items such as insurance, management, vacancy reserve and your tax reserve. Total monthly outflow is the mortgage payment plus operating costs.
Cashflow and yield formulas
Rent means income to the landlord excluding service advances paid by the tenant. Cashflow = rent − operating costs − mortgage payment; the mortgage is subtracted exactly once. Gross yield = annual rent / purchase price. Operating yield (NOI before financing) = annual rent after included operating costs / acquisition basis. Unknown included costs keep cashflow and operating yield as upper bounds. Break-even rent accounts for vacancy reserve exactly once.
Target prices and negotiation gap
Target-price hints are deterministic scenarios: price for neutral cashflow, price for 4% or 5% operating yield, and a broad fair range from model assumptions. They are not sold-comparable valuations.
Rental/investment score
The investment score uses visible rules for gross yield, operating yield, cashflow, renovation risk, property age, ownership, and leverage. Negative cashflow caps keep weak rental economics from receiving a high score.
Profile score vs investment score
Family or first-home profiles can improve own-use fit, but the rental/investment score remains separate. A flat can be strong for living and still weak as an investment.
Input confidence and draft state
Confidence checks whether key assumptions are verified, model-based, manual, or missing. Low confidence should appear before the headline score in reports because weak inputs can make a score look stronger than the evidence.
Market and source context
ČSÚ, ČNB, RÚIAN/ČÚZK, the Ministry of Finance rent map, geodata, and manual comparables support context and verification questions. They do not certify market value, legal status, mortgage availability, or technical condition.
One buyer profile for every home
The home comparison applies the same available cash, monthly housing limit, minimum reserve, mortgage assumptions, and requirements to every apartment. Monthly cost combines the mortgage, owner fees, utilities, a maintenance reserve, and insurance when you enter it. Cash needed combines the down payment, renovation, one-time purchase costs, furniture, moving, and the reserve you want to keep.
Verdicts, requirements, and unknown data
A confirmed budget, reserve, or required-feature failure can exclude an apartment for now. An unknown required fact or missing critical cost produces an undecided result rather than a false pass or zero. Near-limit or partly verified apartments are marked for verification before viewing. Data completeness never improves apartment quality by itself, and the viewing order is not a professional purchase recommendation. Comparison order proceeds from required conditions through met preferences and financial completeness to known monthly costs and reserve. A remaining tie uses earlier addition, then stable ID; this only makes the order deterministic and does not improve the assessment.
Exact investment-score rules
These figures come directly from the deterministic registry used by the calculator. Bands are evaluated from top to bottom and the final score is clamped to 0–100 points.
- Methodology version
- v1
- Base points
- 50
| Condition | Band |
|---|---|
| ≥ 75 | Strong |
| ≥ 60 | Interesting |
| ≥ 45 | Mixed |
| < 45 | Weak |
| Condition | Points |
|---|---|
| ≥ 6% | +18 |
| ≥ 5% | +12 |
| ≥ 4% | +5 |
| ≥ 3% | -5 |
| < 3% | -15 |
| Condition | Points |
|---|---|
| ≥ 5% | +18 |
| ≥ 4% | +10 |
| ≥ 3% | +2 |
| ≥ 2% | -8 |
| < 2% | -18 |
| Condition | Points |
|---|---|
| ≥ 5,000 CZK | +18 |
| ≥ 0 CZK | +10 |
| ≥ -3,000 CZK | -4 |
| ≥ -7,000 CZK | -12 |
| ≥ -12,000 CZK | -20 |
| < -12,000 CZK | -30 |
| Condition | Points |
|---|---|
| Renovation above 12% of purchase price | -15 |
| Renovation above 8% of purchase price | -10 |
| Renovation above 4% of purchase price | -5 |
| Older apartment | -5 |
| Cooperative ownership | -10 |
| Own funds below 15% | -8 |
| Own funds below 20% | -4 |
| Condition | Maximum score |
|---|---|
| ≥ -3,000 CZK | 74 |
| ≥ -7,000 CZK | 64 |
| ≥ -12,000 CZK | 54 |
| < -12,000 CZK | 44 |
Manual values, unknown costs, and confidence
Source precedence is: an explicit user value, a documented or imported value, a model assumption, then unknown. A manual value does not block the score by itself, but it affects evidence confidence. An enabled empty cost is never treated as zero: the result stays preliminary, shows a bound, and names the cost that may change it. A final score requires complete numeric costs and sufficiently evidenced inputs.
Three complete examples using the same calculation
Example A — strong economics
Inputs: Price 3,000,000 CZK; area 50 m²; personal ownership; new build; own funds 40%; rate 3%; term 30 years; rent 35,000 CZK/month; building costs 2,500 CZK/month; vacancy 5%; maintenance 1,000 CZK/month; insurance 500 CZK/month; management 0 CZK/month; tax reserve 6,000 CZK/year; renovation 0 CZK.
Result: Mortgage 7,589 CZK/month; current outflows 13,839 CZK/month; cashflow 21,161 CZK/month; break-even rent 12,725 CZK/month; gross yield 14%; operating yield 11.5%; score 100/100.
Point breakdown: 50 base +18 gross yield +18 operating yield +18 cashflow = 104, clamped to 100 points.
Example B — mixed result
Inputs: Price 4,000,000 CZK; area 55 m²; personal ownership; older apartment; own funds 20%; rate 4.8%; term 30 years; rent 17,000 CZK/month; building costs 3,000 CZK/month; vacancy 5%; maintenance 1,500 CZK/month; insurance 500 CZK/month; management 500 CZK/month; tax reserve 6,000 CZK/year; renovation 0 CZK.
Result: Mortgage 16,789 CZK/month; current outflows 23,639 CZK/month; cashflow -6,639 CZK/month; break-even rent 23,989 CZK/month; gross yield 5.1%; operating yield 3.045%; score 47/100.
Point breakdown: 50 base +12 gross yield +2 operating yield −12 cashflow −5 age = 47 points.
Example C — weak cashflow
Inputs: Price 6,000,000 CZK; area 60 m²; personal ownership; older apartment; own funds 20%; rate 4.8%; term 30 years; rent 24,000 CZK/month; building costs 4,500 CZK/month; vacancy 5%; maintenance 2,000 CZK/month; insurance 500 CZK/month; management 1,000 CZK/month; tax reserve 6,000 CZK/year; renovation 0 CZK.
Result: Mortgage 25,184 CZK/month; current outflows 34,884 CZK/month; cashflow -10,884 CZK/month; break-even rent 35,457 CZK/month; gross yield 4.8%; operating yield 2.86%; score 22/100.
Point breakdown: 50 base +5 gross yield −8 operating yield −20 cashflow −5 age = 22 points.
Sources and data boundaries
BytScore combines entered apartment data with selected public context sources. These sources support assumptions; they do not turn BytScore into a professional valuation, legal advice, mortgage advice, or tax advice.
CSU DataStat CEN0402
Broad open-data context for average apartment purchase prices by region or selected municipality.
CSU DataStat CEN0401
Broad apartment price-index context for recent market movement. It is a trend signal, not a sold-comparable appraisal.
CSU DataStat CEN0202B
Residential construction-cost context used to explain replacement-cost pressure and macro risk.
Ministry of Finance rent map
Official model-rent context used when area and address or location are available. It is labeled as model rent, not guaranteed market rent.
CNB ARAD
Interest-rate and macro context where available. User-entered mortgage assumptions remain the source for the financial model.
RUIAN / CUZK
Address normalization, municipality, cadastre/district, match confidence, and map context when available.
PID open stops
Prague public-transport stop context used as a location-check helper where available, not as a direct valuation input.
CHMI air quality open data
Environmental context where available. It helps surface questions to verify, not a purchase recommendation.
Geoportal Praha
Prague open-data layers used for local context where available.
VUV flood zones
Flood-zone context used to raise verification questions where available.
Prague noise maps
Noise context for Prague locations where available. It is a risk prompt, not a final technical assessment.
Manual comparable listings
User-provided or manually checked listings can support assumptions. BytScore does not treat asking prices as sold-price proof.
Valuo API
Planned paid Data Plus enrichment only. It is listed as a future provider boundary and is not active in the current score.
Valuator
Planned paid Data Plus enrichment only. It is not active in the current deterministic score.