When I was in a situation like this I said: I pay X for renting a room and it's my budget. If you want to rent an apartment together, you have to pay the rest or wait till I'll find a full-time job. The same was with food. He ate twice as much as me, so I couldn't imagine paying 50/50 and sponsoring him food, when I was a poor student.

You shouldn't make your financial situation worse just because your partner probably wants to live in a good apartment.