I am in a committed relationship -- but for various reasons don't want to get married. I just bought my first apartment for $200,000 on a 30 year mortgage. My girlfriend will be living with me but her name is not on the mortgage. We are trying to figure out a fair way for her to help contribute to the mortgage payments. Maybe we will eventually get married, maybe we will eventually break up, who knows. In the meantime, it would be great if there was a way for her to build equity while helping making payments.
For instance, perhaps I could track how much of the principal she has paid off each month and then (informally) agree that I owe her this money. I don't want to set up corporations or pay a bunch of money to lawyers to setup complex ownership schemes. I'm looking for something simple, legal, reasonably formal, easy to setup and tax efficient.