Welcome to the forums. First thing to watch out for is Balrgn buying that Argosy before you get a chance to purchase it. Word's out he's cornering the market on Argosy's.
Check it out as if you are buying a home, you will be living in it. How are the electrical systems, appliances, furnace, plumbing, holding tanks? Any leaks around the windows, door, ceiling seams, fan, vent? How solid is the floor? Have you taken off the mattress and looked under the beds. Is there any mold or mildew present? What does it look like when you shine a bright light into the cabinets, drawers, closets? Frame solid, any rust or sag? Tires in good shape, how old are they. Even tires with good tread can be bad, dry rot. Any dents on the outer skin? How many owners? What kind of use has it gotten? A trailer needs to be used and it really is better to find one that has been in constant use than one that has sat unused for years.
Good Luck and please post some pictures when you buy it.
1994 30' Excella 1000, Chummy III- Ford Excursion- 7.3 Turbo-diesel