Buy a condominium to build wealth?

That depends on your marginal tax rate and the surplus from the rental.

Rental income (gross) per year
minus ancillary costs (gas/water/electricity/property tax/maintenance)
minus depreciation 2% of the acquisition costs (2.5% for construction years before 1925)
minus interest expenses for the rented property
= surplus from renting and leasing

multiplied by marginal tax rate = tax
You can roughly check your marginal tax rate in the chart on Wikipedia.

The apartment is only included in the financing if it is also used as collateral. This is of course only possible if the apartment is, for example, paid off or if there is enough room for borrowing. An apartment that is fully financed obviously does not represent any value.

If you really want to build capital with real estate, then buy shares of real estate companies. Why do you want to buy an apartment at today's high prices with exorbitant additional costs (only one, concentrated risk)? How many years' rent will the apartment cost you? What return do you expect? What risks do you see?

You are right about that. But with stocks, you also have the risk of losing your money. What would be, for example, a real estate company where one could consider buying stocks?