You can sell, but you'll get way less for a house that has a tenant, because the new owner can't kick them out. I know someone that bought a house for a really great price, because it had a tenant that had lived there for 50 years or so. It was basically a 10 year waiting game until the tenant died (he was old when this person bought his place). But after that he sold the place for almost double what he paid. I do have to add that in those 10 years the housing market also went up a lot.

I want to add it might seem I like landlords, I don't, but if we want to get mad at someone it should be the system we accepted as a people.