Wow! Seems like you got a great cage!!!!

If its rusted/old, I would recommend getting it painted, because if the paint is off, it could possibly be dangerous for the birds. I have no idea where to get safe paint from though. Normal paint would be dangerous for the birds. You'd need to use the non-toxic paint cage manufacturers use to paint bird cages before they sell them. I really have no idea where you could get that from.