You refer to pull outs. Most call them slide outs. I think slide outs are great and the amount of creature comfort they add is well worth it my opinion. I haven't had one problem with mine sense 2005. Sounds like a toy hauler or regular 5th wheel would suit your needs just fine. I think you could find either for 20k nicely equipped, but you may have to look awhile. In my opinion finding the right one used will be much more reasonable than finding a super cheap one and modifying. Now about that deck? I just don't know about the deck unless you plan to stay for long periods of time. Then of course you could build something you could break down and put in your garage. They do make screened in rooms for RV's though. JMHO