Dwellers have good bones, and if you can negotiate a discount, more power to you! Mass production has its flaws in RVs, just like any auto manufacturer or home-builder. You'll likely have to navigate a couple issues if you buy a Dweller, but nothing that wouldn't be a deal-breaker, especially if you do get that discount, like Obsessed recommends (it's good advice to look for last year's models).
As for delivery inspection, I'd want to check for:
- Lug torque (a few have been over-torqued; would be problematic to change a tire in the field)
- Gas strut functionality (make sure things that are supposed to open stay open, and close without too much trouble)
- Latch/slide check around the trailer
- Trailer "lean" (look at the front of the D15 and see if it's leaning when parked; I think this can be fixed by switching the side the tongue jack is mounted on)
- Bathroom caulk check (if they've been sitting on the lot for a while, you might see the seams spreading a bit)
- Propane line check (make them light the stove)
- Plumbing leak check (run the sinks and shower, then check under the bed and dinette for any sign of water)
- Tire pressure before you take it home; should be pretty high for the tow on the road (I think it's 72psi?), and you can adjust it as you see fit
- Rear brake light/turn signal check when hooked up to YOUR tow vehicle (should be done before EVERY trip, but make sure it's all working while you're still there)
Anyone else got other things they can think of?
I highly recommend becoming your own mobile RV mechanic regardless of brand you purchase. I've yet to see a thread of any brand of trailer that hasn't included owners making mods or fixing stuff, even Kimberley and Trail Marker. Kingdom might be the exception so far, but that's only because the mods have been designed into the plan real-time by the prime user.
In almost every fix I've come across, doing it myself has taken far less time and effort than taking it to the dealer for warranty issues. Nothing has been much more expensive than the gas getting back and forth to the dealer would have been, either. And you get to learn a bit more about your trailer.
Campers aren't all that hard to work on, and most fixes and mods are simplified with a YouTube video. The bigger rigs are actually easier in many respects because you've got room to work with for plumbing, wiring, and storage solutions. D15s are cool. If you don't need the bunks, though, I think D13s are even cooler, but I'm definitely biased. Good luck with whatever you get!