Why does investing in multi-family apartments make money? Grant Cardone answers your questions right here. Single family homes may sound like a great investment. But one of the things you have to look at is the amount that you spend per unit. For instance, if you buy an $80,000 house as a rental property, how much would a comparable apartment cost for the same monthly rental income? For that $80,000 house, you may be able to charge $600 per month in rent. But an apartment that rents out for that same $600 per month may only cost $15k to $20k per unit. So you could get 4 separate apartment units for the same price you paid for that $80,000 house. How good of a deal does that house sound like now?