Guide: Apartment Building Simulator

An apartment building (immeuble de rapport) is an entire building composed of multiple rental units (studios, 1-bed, 2-bed, 3-bed apartments...) owned by a single owner. Unlike buying a flat in a condominium, you own the entire building from walls to roof.

This is a fundamentally different strategy from single-unit investing. Economies of scale are significant: one notary deed, one property tax bill, no condominium fees (you are the sole decision-maker). Risk diversification is natural: if one unit is vacant, the others continue generating income.

In return, the entry ticket is higher (often EUR 200,000 to 500,000 in provincial France) and management is more complex. This type of investment is suited to intermediate to advanced investors who already master the fundamentals of rental investing and wish to scale up.

The simulator produces a comprehensive analysis at two levels: an overall building view and a unit-by-unit breakdown. This dual perspective is essential for managing your investment.

• Overall profitability: gross, net and net-net yield for the entire building, as if it were a single investment.
• Per-unit profitability: each unit is analyzed individually. Identify the best-performing units and those dragging overall profitability down.
• Global and per-unit cash flow: the building's total monthly cash flow, then the breakdown by unit. A single unit can run at a deficit if others compensate.
• Vacancy analysis: simulation with partial vacancy (1 unit vacant out of 5, 2 out of 5, etc.). Unlike a single flat where vacancy = 0% income, a building continues generating income even with one or two vacant units.
• projection over 20 years: equity evolution, repaid capital, cumulative cash flow, impact of rent and property appreciation.
• IRR (Internal Rate of Return): the overall performance integrating all flows (purchase, works, rents, expenses, taxes, resale).

Apartment buildings open the door to optimization strategies unavailable with single-unit investments. Here are the main approaches to maximize your investment value.

• Buy-renovate-optimize: purchase a discounted building (vacant, poorly maintained), renovate, re-let at market rents. The value created can reach 30 to 50% of the initial investment.
• Space conversion: transform the attic into a studio, convert a vacant commercial unit into housing, turn the courtyard into parking. Every unused square meter is lost income.
• Large unit subdivision: an underdemanded 4-bed apartment can become two highly sought-after 2-bed apartments, with combined rent 30 to 40% higher. Verify technical and regulatory feasibility.
• Switching from unfurnished to furnished: convert units to furnished rentals for higher rents (+15 to 25%) and more favorable taxation (LMNP depreciation).
• Rental deficit strategy: for buildings requiring major works, the rental deficit allows deducting up to EUR 10,700/year from global income. Ideal for high tax brackets.
• Value uplift through refinancing: after renovation, have the building revalued and refinance to extract cash and fund a new investment. This is the BRRRR strategy (Buy, Rehab, Rent, Refinance, Repeat).

Apartment building investment is powerful but carries specific risks. Here are the most common mistakes made by first-time building investors.

• Underestimating the renovation budget: older buildings often have surprises (roof, frame, general plumbing, electrical upgrades). Always add 20 to 30% margin on the initial works budget.
• Ignoring structural issues: a facade crack, a sagging frame, damp foundations. A complete structural survey is essential before purchase. The cost (EUR 2,000 to 5,000) is negligible compared to the risks.
• Overestimating rents: base your calculations on actual market rents, not optimistic projections. Check local listings, ask local agencies, verify prices on reference sites.
• Neglecting vacancy: even in a multi-unit building, cumulative vacancy weighs heavily. Budget 5 to 8% annual vacancy for a well-located building, 10 to 15% in less sought-after areas.
• Underestimating management complexity: managing 5 to 10 tenants, ongoing maintenance works, incidents, administrative exchanges. If you are not ready to invest time, plan for a professional property manager.
• Paying too much: an apartment building is only interesting if the price per sqm is significantly below the retail market price. Aim for a minimum 15 to 25% discount.
• Forgetting about resale: a building sells less easily than a flat. The buyer market is narrower (investors). Plan for a long holding period (10 years minimum).