Along with the engine/tranny there can be a lot of problems with older motor homes. Some you can live with, some not so easily. I've got a 1990 Holiday Rambler and really like it. But it does require a lot of knowledge and maintenance to keep everything going. If you can do it and like to do it, no big deal. If I would have paid for everything that's been done over the years it would probably cost more than I paid for the motor home.
I guess you pay one way or the other, but sometimes problems can be real trip killers.