I just purchased a 2008 Kendon trailer for US$1,000.
It required some paint $30, cosmetic, three new tires $180, and a replacement ramp $65 (from Revzilla), safety chains $30, and some reflective stickers for the frame $60.
As noted by the others, check to ensure the bearings have been greased. My trailer came equipped with bearing buddies that allows one to inject grease using a simple grease gun-nipple arrangement.
My only other recommendation is that you stand the trailer up vertically, as it would be stored, and inspect the underside to ensure that their are no cracked tubes. I have seen some with this type of damage.
If you do not need the trailer to stand vertically for storage, consider this copy-cat brand:
Trinity 3-Rail Motorcycle Trailer MT3
They are literally half the price and appear to be made just as well.
In case your interested, I know of a 2008 Kendon for sale near me in AR that is literally in mint condition, stored in a garage and needs nothing other than a new owner. The guy is asking $1,900; he has had it for sale for about a year.