You know that renting, or most of it goes through a contract, let's say 2-10 years. It's really not that hard to rent out your house.
Back to thread starter. I would laugh my ass off if you really went back to your parents. No offense really, not trying to be rude but you just failed big time. You seem to have really nice parents, they want actually to take you back and straighten up your life, even though you left them. It's nothing wrong staying with your parents, stay with them. Of course u around 30+ it would feel a bit odd, but w/e. You actually had the chance to stay with them as they seem nice enough to want you back. But you regardless went out and thought you could live your own life as you wanted but failed miserable. The problem is, if I was the parent, I would have said to you, stay in my home as long as you want. You don't have to worry about food, rents etc. Finish of your studies and feel free to leave whenever you're ready, but when you leave .. you're not supposed to come back. With that I mean it's okey to come back and see your parents to sleep over 2-3 days, or a week for sure. But you will then have to stand on your own feet and live your own life.
Why did you leave in the first place? That is what I can't undertand. Some parents are just way too nice, they have to man up and say that " stay as long a you want, but when you leave you're only comming back as a guest, not to stay." Sounds harsh but that's life, you can't expect your parents to pay of for your the whole road. Your problem was that you left before you were ready, you thought that you had so much with those 300k that you could just live your life.
I'm not trying to pick on you, be rude or anything . I'm just trying to put out a constructive happening and problems you've gotten from leaving the house. Why don't just get a job? Get a cheap rent for 400-500 bucks, get a job and live there. You could easily make a boundle of cash while studying. I myself make up quite a large boundle, to not brag no number is given. Even though I go to school. I wake up 7, go to school to 3-4, straight from there to work up to 10 and come home pretty late. And that 5 times a week. If I can, you can. Just stop being a slacker, I mean you bought a car and other stuff with that last 100k. Maybe that was your problem? Although I found it pretty good that you actually managed to buy off a house and rent it out, + for that.
Summary: Don't go back, stay with your brother until you find a job. As soon as you find a job, start searching for a place to live and you can pretty much maintain a living with school + 3-4 day workdays. It's not going to do any harm. Going back to your parents will just show that you failed. Don't do so. I still admire your parents, they actually want you back..