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.