Really, anything can be fixed pretty cheap. Plastic will run you 250$, tires and rims about the same.... The big thing with the 350X is does it smoke? does it tick and does it get up and go....
Low oil levels and backwards filters (Hi TANK!!!!!!!!!!!!!) will ruin the head and thats mucho bucks to fix.
We can talk about bearings and bent forks and rusty tanks - thats all common stuff to look at any purchase. It's an 86 so the frames usually don't have a problem. But of course, look it all over, take your time and point out any beat up stuff.
Everything else is gravy.
Beat up 350X - 300$ to 800$. Expect to pay 1000$ to 1700$ for a nice 350X and hundreds more for OEM, all stock and mint.
GREAT TIME TO BUY!!!!!!!!!!!!
All our government does is distract us while they steal from us, misspend our tax $ and ruin our country