Several years ago we bought a truck camper from a dealer who advertised on e-bay. We checked their BBB rating, then simply called them and negotiated over the phone. Actually ended up with a better deal then they were offering on e-bay.
Had a similar experience with a house. I would recommend starting by sweeping/vacuuming everything you possible can - wearing a dust mask and rubber gloves - then spraying every possabile surface with a good disinfectant/cleaner. Depending on how th...