1967 Terry key

Call every RVer you know to come look at the new jewel. Ask they bring their keys.

Have a locksmith re-key it (just like if you were buying a house), or change the assembly out for a new one.

Any chance of posting pictures? Inside and out.

I hope he is not buying it without seeing inside? Yes, go with a lock smith. Or if you feel adventurous he may be able to remove all the screws holding the door frame in place and gently remove the foor in the frame

We've been inside it. Many RV locks are easy marks for amateur lock pickers. :) The inside was recently "gutted and refurbed", all new walls and new ceiling by a RV shop.

Didn't really want to replace the knob unless we can find a retro replacement.

We could go the locksmith route.

Why doesn’t your friend post these inquiries?

Missing key...locksmith.

If the door is unlocked remove the knob and take it to a locksmith for a rekey.

If you want to save a little bit of money check with anybody you know that has teenagers and see if any of them know how to pick locks. It seems a fey years ago all my kids and their friends all got into picking locks. So it's entirely possible the teenagers in your area did the same. If you can get the lock picked have them leave it with the cylinder turned and then take it to the locksmith for the rekey. Let them know that the cylinder is already turned which may save on paying the locksmith to sit and try to pick the lock.