I'm afraid that unless you can do the work yourself, you are in for a pretty expensive repair. Most RV repair shops charge upwards of 80 to 125 bucks an hour for labor, not including material. Is this an honest to goodness soft spot or does the floor just give some in that area? I had a Coachmen TT that had some give in the floor from the time it was brand new, but it wasn't rot.
Mike in Tennessee
Former 2 time FR owner
2007 Crossroads Cruiser 30QB Fifth Wheel
2008 F-250 Lariat 4x4 6.4 Powerstroke
Firestone Ride-Rites w/cab control