I always offer the same advise, buy used. Let someone else lose the first couple of years depreciation. That is where the big bite is that hurts the most.
For that budget you will have a ton of coaches to chose from. As someone else said a good place to start is PPL there in Houston. There are coaches out there that are 2 to 3 years old that look like new. Ours was 7 years old when we bought it for about one third of your budget. Found it on RVTrader.com. It had been kept in a heated garage all of it life when not being used and was in mint condition. The Cummins is a great engine and you will have no problem finding one(may not be a 500hp but that is a lot of engine), just get a floorplan you like and go with it. I only have a 330hp but I always get where I want to go.
Good luck and welcome to the forum.