A property project is about more than finding a home and securing a mortgage. Borrowing capacity, often presented as the starting point, covers only part of the financial equation. Service charges, planned renovations, energy costs and temporary income loss all affect whether a purchase remains affordable over the medium term.
Measuring the gap between the theoretical budget (what the bank will lend) and the real budget (what the household can afford over ten or twenty years) provides a more reliable framework.
Theoretical and real-estate budgets: gaps to plan for
Most property guides stop at calculating borrowing capacity: income minus expenses, subject to the debt-to-income ratio capped at 35% since January 2022. This calculation gives you a maximum monthly payment, not a project budget.
Several costs are left out of the bank’s assessment. Bringing them together in a table makes it easier to see their relative impact.
| Budget item | Included by the bank | Real impact on the budget |
|---|---|---|
| Mortgage payment | Yes | Main expense, capped at 35% of income |
| Notary fees | Partially (covered by the down payment) | Account for a significant share of the purchase price for older properties |
| Condominium fees | No | Vary by building and can rise sharply after renovation work is approved |
| Renovation or compliance work | No (unless covered by a dedicated renovation loan) | Often underestimated before signing |
| Energy costs | No | A poor energy rating increases monthly bills throughout the ownership period |
| Property tax | No | Can be twice as high from one municipality to another for a comparable property |
| Reduced income (leave, unemployment, part-time work) | No | No buffer is built in if income falls after the purchase |
This table shows that the mortgage payment is just one of seven items in the real cost of buying a property. Buyers who use their full borrowing capacity without setting money aside for these expenses can find themselves under financial strain as soon as they receive their first bill for façade repairs or boiler replacement.
For information on simulation tools, financing assistance and rental investment schemes, Web United’s real estate website brings together resources organised by project type.
Condominium fees and renovation work: two costs that can throw a property budget off track
Condominium fees are listed in the property advert, but the amount shown reflects the routine charges for the previous year. It does not include work approved at the general meeting or exceptional calls for funds.
A building from the 1970s whose façade, roof or pipes have not been renovated may require calls for funds amounting to several months’ mortgage payments. Reviewing the minutes of the last three general meetings before signing a preliminary sales agreement can help identify work that has already been approved or is under consideration.
- Check the mandatory works fund (ALUR law) and the amount set aside in the property manager’s accounts
- Request the comprehensive technical assessment (DTG), if available, or the multi-year works plan (PPT) if one has been adopted
- Compare routine charges with those of similar condominiums in the same neighbourhood to spot unusually low fees (which may indicate deferred spending)
- Include an annual allowance for renovation work in your budget, even if none is currently planned
A budget that can withstand unexpected costs includes an allowance for renovation work from the outset, even for a property that appears to be in good condition. Shared facilities (lifts, central heating, waterproofing) have predictable replacement cycles.
How the energy rating affects the real cost of a home
The energy performance certificate affects costs in two ways. First, a property rated F or G will have significantly higher energy bills than one rated C or D. Second, the gradual restrictions on renting out energy-inefficient homes reduce both the rental value and the property’s resale liquidity.
Buying an energy-inefficient property without budgeting for energy-efficiency upgrades means underestimating the true purchase cost. The cost of insulation, replacement windows and doors, or a new heating system should be included in the project’s overall budget.
Financing simulators and tools: what they measure and what they miss
Online simulators offered by banks and mortgage brokers calculate the maximum monthly payment, loan term and, sometimes, the total cost of the loan. They factor in the interest rate, borrower’s insurance and down payment.
Their limitation lies in what they do not model: how fixed costs change after the purchase. No standard simulator asks about condominium fees, the energy rating of the property or the local property tax rate.
To make up for this, it is useful to create a personal spreadsheet that adds together the mortgage payment, condominium fees, property tax, estimated monthly energy costs and an allowance for renovation work. The amount left over after all these costs have been paid gives a more reliable picture than the debt-to-income ratio alone.
Down payment: beyond the bank’s minimum
The down payment generally covers notary fees, which amount to around one-tenth of the purchase price. Using all your savings to increase the down payment reduces the cost of borrowing but leaves you with no reserve for unexpected expenses.
Keeping an emergency fund equivalent to several months of mortgage payments provides a buffer against setbacks (job loss, sick leave, separation). The right down payment is not the largest possible one, but one that leaves you with an adequate safety net.
Long-term property project: stress-test your financing plan
A sound financing plan should be tested under pressure. What happens if household income falls by twenty per cent for a year? Will the mortgage payment still be manageable alongside routine expenses?
- Model a reduced-income scenario (part-time work, the end of a fixed-term contract, parental leave) and check that the remaining income covers everyday expenses
- Check whether you can reduce your monthly payments, an option offered by some mortgage agreements
- Plan for energy or condominium fees to rise over the next five years
This kind of stress test does not appear in any standard guide. It turns a static budget into a dynamic forecast that can absorb fluctuations without putting the project at risk.
The 35% debt-to-income ratio is a regulatory ceiling, not a target. Staying below this threshold with a comfortable margin gives you the flexibility to absorb changes in expenses and income over the life of the loan.
