Oh My! You should watch out for falling in love
Besides that, why only 3 months? I would ask her that also if there is a possibility it would be longer, is there a contract stating she will be back for him? I know these sound pessimistic but this sounds like an odd situation to me. Also, how will you be able to contact her should he need vet visits, etc. Is she giving you a 3 month supply of items he will need, or leaving you with money?
Also, the bathroom is a good idea, lots of people do that for safety reasons. It sounds like you would be the perfect foster mom for him! Your apartment allows pets right?
Good Luck and keep us posted