Is it possible I could end up owing Unison back less money at the end than I received at the beginning?

Yes. Unison is not a loan; we are invested in your home alongside you, so we win and lose together. Though such cases are not common, with significant decline in your home’s value–something neither of us are looking for!–it is possible that the value of the agreement, and your ending amount due to Unison, would be $0. It’s this feature along with the absence of any monthly payments that distinguishes an equity sharing agreement from a loan.