in addition to my previous comment, I would like to say that if a house starts out livable (some basic heat, some basic running water, and a roof), then the cost of fixing it up can be a lot lower because a homeowner can live there and fix it up themselves gradually. you can get away with a lot of non-permitted renovations when you live there and do it gradually. if you hire a crew to come in and gut it, you will get shut down if you try to re-plumb, re-wire, etc. a house without a permit. but if you want to re-run the electrical to a room in your own house on the weekends, nobody is going to know or care.

so, if you're not making much money, you can get a cheap place that is minimally livable and gradually fix it up for probably half the cost of doing a full gut, though you probably won't get as much resale value out of it because it will still look old, even if you have replaced the plumbing and such.