How do people upvoting this imagine this would work? There are essentially two things you could buy, and they’re available independently: servicing rights (“You are responsible for talking to the homeowner and receiving checks then sending them upstream”) and the economics of the mortgage.

If you beneficially own the economics... well, great, your arch enemy is theoretically paying you money, but you have no options to screw with them. You own an extremely regulated specialty financial product. This is similar to the misconception that stock in Google entitles you to just walk in and take a computer in exchange.

If you buy the servicing rights, you have much more surface area to be an incompetent servicer, but again extremely regulated and you’re pricing yourself to being sued by the homeowner, the GSEs et al who set up the securitization program and zealously defend it, and potentially even the entity owning the economics.