We hear that many rv have issues with quality. Things breaking down over time
For every negative story you'v heard - there are probably 10 positive stories. I've had 3 TT's over the past 24? years and never had to take it to a dealer for work (warranty or otherwise)
Sure - stuff breaks - but it's simple to fix. For instance - this
past week-end, the rear tail-light broke. Shot off to Camping World, bought a new one for $11 - got back home and 30 mins later it was fixed.
If you want to build an RV - it sounds like you have mechaniocal aptitude, so fixing an TT/RV when it breaks should simple for you.
(BTW - I'm excluding water issues in this discussion - that is a whole different topic)