I think if you aren't married everything should be 50/50 unless the guy is totally generous and says he wants to pay for most of it...but Legally as long as you are on the rental agreement or lease you are only required to pay half if you are considered roomates (rent;utilities). Now food on the other hand, you may be responsible for your own, and he his....but thats my take on it.
I am married so my hubby pays rent, food and his own bills. I pay the Utilities, Cable, Phone, Internet, Insurance and my own bills...so it works out pretty nice! But like I said everyone does it different.