As soon as you get it, recaulk all of the window, door and applicance frames on the outside. Use a good sealant, I've used Quad in the past. It's a pain to work with but was told by an RV dealer that it was one of the best. We had a very bad experience with a Coachmen TT that we bought new in 2003. Within 3 years, I noticed a soft spot in the floor, under the carpet near the entrance door. At the end of the 4th season I decided I better take a look at it and see what was going on. I removed the bed, couch, water tank (under couch) and all of the cabinets in the master bedroom. Then I pulled up the carpet and discoverd 4 areas of extensive rot in the floor. I had to use most of a 4x8 sheet of plywood to fix all of the rotten places and even had to sister in some extra floor joists. There was absolutely no visible signs of leakage anywhere on the walls or ceiling and I had no idea of the damage until I pulled the carpet up.
I'm not saying this is unique to Coachmen either, and I hope you have better luck with yours.
When we traded this leaker on a Jayco, the first thing I did was reseal all of the openings and many of the seams just to be safe.
Good luck and happy camping!