I'll be honest with you mate, once you ride it, you will buy it, even if it's ready for the knackers.
The pipes are not a big problem, there is an aftermarket company that sells stainless steel pipes that will never rust. Can't remember who it was, but you might be able to find mention of them if you use the search engine on this site. As long as the frame is not rusting and it runs well, the bike will be alright.
Another bit of advice, plan the longest possible route home incase you do decide to buy. You are not going to want to get off it any sooner than you have too.

Let's hope there's intelligent life somewhere in space 'cause it's buggar all down here. -- Monte Python