RTO balances

I was thinking through this, and I think I answered my own question before I even pose it. But I will just confirm. When looking to purchase and valuing remaining note balances on rent to own contracts, does anyone use a specific %? The more I think of it, it is not too far different from a pure rental since some do walk away, in which case lot rent only is the clear valuing mechanism. But practically I think there is some value there, just not sure what if anything to pay for it. Before digging in too hard, we would all want to think of it from the sell side too some day.