The profit is compensation for the risk. The mortgage and property taxes and maintenance are due no matter what - can't find a tenant, tenant doesn't pay, tenant flushes paper towels down the toilets every day etc etc.

If there was no profit there would be no landlords. Some might say that's great. But it would be a world with less flexibility, with fewer choices. Don't like your job and want to move? Split up with your partner and need someplace to live? Moved to a new city and don't know where you want to put down roots yet? At college for 4 years? Don't want to deal with house maintenance? "F** you, buy a house anyway". That's what we'd have if there was no rental housing.