I don't know how they can build the house before the chassis, just doesn't make any sense to me.
"I can still get out of the sale" Are you sure? Exactly does any paperwork you signed say and how long if you've given them $?
Trying to be helpful: Never buy a RV that you haven't personally inspected and driven and never give them upfront $ until you are ready to buy. If you don't have RV experience hire an independent professional inspector and get a full report. Plus have your own PDI (Pre Delivery Inspection) that includes everything. With your work clothes check everything including underneath for damage, rust etc. This will cost you a few hundred bucks and transportation but it can be pocket change compared to the potential for very expensive repairs.
