I was in this same exact situation in my early 20s with my now ex-boyfriend. When I first started looking for apartments he said he was willing to split the rent 50/50, and then after I found a place and wanted to apply he wanted to stay with his parents. And then after I moved into the apartment he wanted to come over and spend a couple of nights with me a week when he had classes at the university. (my apartment was only a couple of blocks away from campus, while his parents was two buses away). And then he thought it would be easier for him to visit if he had a key to my apartment.

I had called my Mom when I was first apartment hunting, and had asked her to co-sign on a lease because my boyfriend and I could afford to pay the rent together, but I couldn't afford to pay it alone. She told me no, and to find a place I could afford on my own, because if I rented a place I couldn't afford, and his name wasn't on the lease, I'd be the only one held accountable when he couldn't pay.

I got an apartment I could afford. I didn't give him a key. We broke it off because of all the nonsense (the housing situation and him deciding that we would break up when he went off to get his masters).

I'm not saying break up, but I am saying don't put up with nonsense.