Apartments in our area have a maximum return of 3%. You’re better off with an ETF.
The (absolutely illogical) approach, however, is that many people invest the majority of their wealth in real estate, but are quite hesitant with stocks/ETFs. I include myself in that and have only about 1/4 in stocks. When you compare this with a (capital investment) condominium in which 100% of free assets flow, the return in € is comparable (equivalent to 12% with ETFs/stocks). Also, depreciation and appreciation of the properties must not be neglected in the comparison. The total return must therefore be calculated from rental income, tax depreciation, and value gain for the apartments and dividends + value appreciation minus capital gains tax for the stocks (I assume that the condominium is held for more than 10 years).