My and and I co-habited for 6 years in Arizona. The house is mine, and he has physically moved out, but still has a lot of stuff at my house. He purchased a very large outbuilding which has power, but no plumbing, to use as a studio while we were together. He's trying to see if there's any way for him to sell or move it, but likely it is too big and he'll just have to take the loss. I don't want or need it.

When we lived together, he paid the utilities but no rent, and we had no written lease.

I have offered to let him use the studio as a storage unit for now, as he has so much stuff that he's trying to move and I just want it all out of my house so that I can change the locks and start to move on. Is there any legal jeopardy for me in allowing him to use the studio as storage for now?

At what point would the building become mine? Do I have to pay him for it?

Thanks in advance, my friends!