House construction. Sell or rent out the condominium?

And where is the 600K for the new house coming from then?

If a condo (depending on the location) has already experienced a significant increase in value, I would bring the property into play as collateral with the bank. This could significantly improve the terms and thus lead to better interest rates. Once the condo is paid off, increase the repayment rate and use the income to additionally service the house.

And where is the 600K for the new house supposed to come from?

That is exactly the problem. Assuming the apartment is paid off and can be rented out for €900. If I can only pay down 2% of the purchase price annually, it would be "only" about €4000 compared to about €11000 in rent assumptions. Since the apartment is fairly new, I have very few advertising/renovation costs that I can deduct. So I would have to pay tax on about €7000. Or am I calculating this wrong?

That is exactly the problem. Assuming the apartment is paid off and can be rented out for €900. If I can only pay off 2% of the purchase price annually, it would be "only" about €4000 compared to about €11000 rental income assumptions. Since the apartment is quite new, I have few advertising/renovation costs that I can deduct. So I would have to pay taxes on about €7000. Or am I calculating this wrong?

What are the 2%? Of what? The taxes are calculated based on all your income, not just from renting.

What are the 2%? Of what? The taxes are calculated from all your income, not just from renting.

By the 2% I mean the depreciation (over 50 years). The apartment originally cost about 220k - proportionate land value (about 20k) = 200k x 2% = 4000€

For taxes, I recommend a tax advisor, old house or condominium with rental income and ancillary costs and depreciation, new house with almost all costs for the home office, he will calculate for a while. Talk to a tax advisor beforehand, after half an hour he will tell you what suits you better.

Who owns the apartment? You or both of you? Otherwise, perhaps sell to the spouse? Would have the following advantages: - Generates equity for the new house - Is exempt from real estate transfer tax - Generates interest on the condominium, which can be depreciated - Generates a higher purchase price, which can be depreciated It should be arranged so that the apartment pays for itself. Thus, it continues to pay itself off, taxes are low, and you have equity for the new house. But this only works if it belongs to only one person.