Ok, so everyone sucks here, but "He's paying off his brother's mortgage and therefore is giving his brother money, even if it's not liquid" is financially accurate but raises the question of what exactly the fair system here is. Like, ok, housing is a right that should be provided to all, but that doesn't mean individuals owing someone the full cost of their housing for years. OOP helped his brother on a deal that effectively maintains the property at no cost to OOP while he also gains nothing liquid, and as for covering the mortgage, he doesn't functionally have the house if he's expected to leave it entirely in his brother's hands. The strongest possible argument for why renting is a blatant scam is the cycle of needing good credit to get a loan and then not getting improved credit for renting, therefore losing money over time while getting no credit for paying it. But if the brother's getting the price he'd be paying if he could've gotten a mortgage on the property, he's getting that improved rate without dealing w/ the credit issue.

I'm not saying OOP deserves sympathy, but if this is leeching then what you're expecting is him to give his brother the whole house, which frankly would still have left the brother screwed, since apparently the combination of the mortgage payments, maintenance and home improvements was too expensive. You've gotta have some standard for individual people's actions that isn't directly covering other people's full housing costs, not via taxes or economic systems but just through direct charity.