My brother (30 ) will never be able to be self sufficient. He actually lives alone but our dad is paying the rent, bills, and allowance. I think it's definitely taking a toll on him and it took him some time to fully come to terms with the hopelessness of the situation. It is especially tough because there is always the question of what will happen in the future if my dad is no longer able to support him, and my mom also dreads the idea of him coming to live with them. He is also getting more and more out of touch with reality due to lifestyle.
The thing is, if my dad was to stop "enabling" him I know for sure that things would get infinitely worse. He'd probably end up homeless and end up being manipulated and taken advantage of by the predatory type of people.