Maybe I underestimate Python mania, but IMHO that is way too much for one with rust on it.
FWIW, you can "remove" active rust, but you can NEVER restore the metal that has been eaten away by the oxidation of which rust is a product.*
If you have to have a Python right now, that rust (probably from a leather holster) can be overlooked. But I would either try to get a better deal of keep looking for one without rust.
*Yes, I know about TIG welding pits and polishing, etc. But we are talking about a Python here, not some exceedingly rare gun that will bring 100 grand after restoration.