Door leaks are very common, especially on older trailers as the weather stripping fails. Windows also. I would check the ENTIRE floor, particularly under the water heater, water tank, access doors, under the bath area....
Replacing flooring is a major project. Really hard if it goes under the built in furnishing. Get a deduct on the price you are paying for this, if possible.
Owning sloppy drinking Boxers all my life (7 todate), all house dogs, I cannot imagine dog bowls causing a rotten floor. I smell smoke.
-"You want to make it two inches - or, if you're working in centimeters, make sure it's enough centimeters for two inches."-Red Green