I think what is enabling depends on the situation. Do you think your son’s struggles with reality would keep him from being independent, even if he stayed sober? Could he even keep in his working knowledge the notion that his housing is contingent on medication compliance? Is he consciously trying to manipulate you so he can underfunction or use?
Depending on the answers, it might not be enabling to help him stay housed. It would just be a parent helping to support an adult child too disabled to support himself.
To Tanya’s points, though, is it feasible for you to house him long term? Is he capable of being a tenant?