I had a real bad experience with this. The girl in question had been my suitemate in the dorm for four semesters so we thought things would work out. We had about the same tolerance for squalor and we liked the same music and had lots of the same friends. But:
First of all she moved into my place, a house I was buying. The rent was half the house payment and it was pretty cheap. She was okay with that.
Four days after she moved in she met A Guy. I’ll call him Alaska, 'cause that’s where he was from. It is also worth noting that her first month in the house was the month of June, in Oklahoma, that the house had air conditioning, and that I don’t mind being hot and I hate air conditioning. My roommate was completely okay with this for four days, until Alaska. He essentially moved in–that’s right, right after she met him.
At that point I had all the disadvantages of a roommate (things disappearing out of the fridge that I had specifically earmarked, say) and none of the advantages, since Roomie and Alaska would get home from work and go straight into Roomie’s bedroom, and stay there only coming out to raid the fridge.
After only a couple of days, it turned out that Alaska was miserable in the heat, not being accustomed to those climes, so could we run the air conditioning.
I was at the time morally opposed to air conditioning, cars, paper towels, and whole bunch of other stuff that’s now becoming once again politically correct. Plus I love hot weather and besides which, running the air conditioning was way expensive, even way back then in the '70s of the last century. But Alaska was just gonna die without it.
So…I taped over all the AC vents in MY room, put blankets under the door so I’d be comfortable, in my own house that I was paying for. And when we got the bill, which was more than the house payment, I thought it was not too fair to split it in half. I didn’t even think it was fair to split it in THIRDS, since I hadn’t ever, ever wanted the AC on to begin with. Roomie pointed out that the bill probably wouldn’t have been so high if it had been the whole house, because after all some of the heat oozed out from under my door, and if I wanted to be hot I could just go outside, but who wanted to be hot, anyway? But she finally, grudgingly said that she and Alaska would pay two-thirds of the electric, even though she didn’t think it was fair, and she was in the smaller room anyway. And it was really unfair since she was paying my mortgage (half of it anyway), so she was getting only a temporary benefit whereas I was putting $$$ toward a long-term asset. And also my presence (!) was cramping their style.
So this gist of this was, after inflicting AC on me in my living room and kitchen during two out of three of my favorite hot months of the year, Roomie and Alaska moved out in August to their own place. Leaving me determined to starve, if necessary, to make the payments on my own so’s I wouldn’t need a roommate.
Honestly, I’ve had better luck moving in with a complete stranger whose name I got from a college bulletin board.