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You say your are looking to do a "full rennovation," do you mean shell-off, floor replacement, rebuild of everything, etc., or more of a superficial sprucing up?
If you are going "full monty," then you may as well buy at trailer that is a field find, with a decent shell, as you are going to rip everything apart anyway. A trailer in this shape should cost less than $3k. There is no sense in buying a "camping ready" trailer, unless you don't intend to really tear into it.