Leverage: The Amplifier Works in Both Directions

One identity governs everything:

Return on equity = r_asset + (D/E) × (r_asset − r_debt)

Our deal: r_asset = 2.76% (net initial yield), r_debt = 4.2%, real equity at completion €8,000, debt €170,000, so D/E ≈ 21×.

On income alone: 2.76% + 21 × (2.76% − 4.20%) ≈ −27%. Leverage is not helping. It is destroying the income return, violently, because r_debt > r_asset. This is negative leverage, and in 2026 it is the normal condition of nearly every German A- and B-city rental: net yields of 2.5–3.0% against mortgage rates of 3.7–4.3%. Between 2016 and 2021 the same flats yielded 3.0–3.5% against 1.0–1.5% debt – strongly positive leverage. That regime is over, and most of the property advice you will read was written inside it. When someone tells you their flat "pays for itself," ask what year they bought.

The same 21× multiplier applies to price. A 2% rise on €178,000 is €3,560 – +44% on €8,000 of equity. A 2% fall is −44%. A 5% fall puts you in negative equity. German lenders do not issue margin calls to performing borrowers, so this is not a forced sale – but it is a real constraint: you cannot sell, and you cannot refinance well.

So the whole case rests on the term with the widest error bars. That is the trade. Make it consciously rather than discovering it in year six.

What flips leverage positive:

• Buy below market. The only lever that is free.
• Higher-yield geography. Commuter belt or small town at 5–6% gross versus ~4% in the city. Genuinely different risk, not a free lunch.
• Time. Rents compound; the nominal loan does not. Yield-on-cost rises even when today's carry is negative.
• More Tilgung. 3% instead of 2% costs €142/month and cuts full repayment from 27.5 years to 21.3, leaving €108,000 owed at year 10 instead of €128,800.

At refinancing, leverage de-risks mechanically – if prices hold. €128,800 against a €217,000 value is 59% LTV, back inside the prime Beleihungsauslauf band (under 60%), worth roughly 20–40bp. But if prices fall 30%, LTV is 85%: you pay a premium, or the bank asks for a Sondertilgung or extra collateral. Model that branch before you sign, not in 2036.