Right, "technically" you're dating a roommate. My old-school thoughts - A makes enough to pay for house and utilities and should until you're married. Its A's house. B can help with food and other consumables. If B wants to help with mortgage, more than welcome to.

I'd be nervous to buy a house together without being married. This is coming from someone who doesnt have a seperate account. Every account my wife n I have is shared. I can't imagine any other way but I know people make it work.

This stuff always gets weird when you're dating your roommate. Talk about it and decide what would make both of you happy. Marriage seems like it solves all the problems.