Hey Cliff,
Get the tires off the ground and give them a spin, if it is quite your OK, if noisy you need to do the bearings. Also check the tire for any play in the wheel, try to twist the tire left to right, there should be no movement. If the trailer is sound and the lights are working, bearings are pretty easy to do but you don't want to be towing far if they are in rough shape. Lights can be a pain trying to trace down a problem. In the past I've just rewired the trailer, should be good for a few years after doing this. If the tires are cracking then replace them. Rust can be a problem depending on the age of the trailer. Find a galvanized one if you can, worth the extra money IMO. My next trailer will be galvanized. If it's a newer trailer with a bit of surface rust, shouldn't be a problem, just a bit of paint to make it look good and slow down the corrosion.
Good Luck!
PS - If you need some help with repairs I can help you out if you need it.