I absolutely think it is fair to ask for some financial help when you have a roommate half the time, essentially. However, do you have a clear picture of his finances? I ask because it may be that he’s living at home to save money for a down payment on a house that you might eventually live in (not knowing how serious your relationship is). I guess what I’m getting at is that I think if he is trying to achieve financial goals you should be mindful of that while also not being trampled or taken advantage of.

I think at the very least you can ask him to help out with utilities, given that you obviously use more water, electricity, etc. with another person there so often. Would he be comfortable taking on a portion of the utilities, paying for more food at your place, and maybe paying a bit more than half of the time when you guys go out? I don’t really think it is fair to ask him to pay for part of the rent, because you pay the same amount whether or not he’s there and he didn’t have a say in where you live (so it might not be the place or amount he would have selected if he were an equal partner in making the decision). I hope that if he’s a quality guy he will be happy to contribute and understand that you’re currently subsidizing a large portion of your time together.