I'm just thinking back to when spouse and I were at the "spending most of the weekend at my place" phase. Granted, he was neither really making nor saving money by doing so, but the thought of asking him to, say, chip in on rent or do more than buy groceries (which we just kind of handled casually) makes me feel...icky, somehow. I know that I saved a lot of money on buses or even the odd taxi because he gave me rides, and I think I would have been utterly stunned to be asked for gas money. I suppose I could see offering, especially if I were renting my car out, but if he'd asked for it... Maybe I'm not seeing this clearly, maybe my age is showing, here, but the way this LW is approaching this situation raises my hackles.

It may also be that I'm assuming the relationship is eventually going to change into something else that involves more finance-sharing. If that's not the case, then...no, I still feel kind of icky about it.