Hi
I'd walk away. Most of theses have rust but as there are so many for sale now and prices are so low you need to find a rust free example. This is the most important consideration. Youtube has a vid of where the rust gets in and is time-consuming (or expensive) to get at in order to repair. A proper engineer should have kept a record of what he'd done (eg at that mileage the g/box fluid should have been changed and documented) even if he'd clearly not done any welding. Rust can be difficult to see - especially for a novice - and any rust is highly likely to be the tip of an expensive iceberg in addition to everything else that will need doing, Well done for finding the rust but that's a bright red flag would be my advice.
