Based on your financial expertise, provide your response or viewpoint on the given financial question or topic. The response format is open.

In a house with shared ownership, if one person moves out and the other assumes mortgage, how do we determine who owns what share in the end?
Let's look at the logical extreme. Two people get a house, no money down, 10 year mortgage. One moves out the day after the closing, and the gal left pays the full mortgage. Why in the world would the one who left be entitled to a dime?  You offer no information about the downpayment or amount paid during the time both lived there. That's the data needed to do any math.