Well, I can tell you that with every FTO there will be problems. Straigh up. Because they are almost 10 yrs old, and if you do find a 100% clean fto, then you are paying a little bit more ofcourse.
There are two sides to this, the first one, you buy this one, and fix it up, and you won't have to worry about the same problems for some time, or if you get another one, these problems may come up in the future...
It's a very tough call, but when i was looking i walked away from a few FTO's that have has oil leaks.
The only big problem that worries me with this fto that you found is the oil leak. Oil leaks can be very expensive to fix. If you want to buy this FTO, make sure you know 100% where the leak is coming from. If it is just from the rocker cover then that isn't much of an issue.
So you can even ask the owner to take it to a designated mechanic so that he can have a look more closer.
Ok, so if it's a major oil leak, then your looking < 1,000 to fix, then while that is being done, you may as well give the tappets/lifters some adjusting, and maybe look at doing some of the other components of a major service too.
Suspension, is hard to determine, I can't really say anything as i haven't had much experience with it.
Brake pads will probably be < 150/200 to replace. ( For Good ones anyway ) New rotors, will be also that much I think so all up for that your looking at around ~ 300....
Umm, rust isn't much of a problem, that can be done like a few months down the track. Mine is still rusty. after over 6 months of ownership
Also if you need to replace a tyre, you have to probably replace two.... so your looking at around 200 a tyre for decent ones.
Anyway, hope that helps.
Good Luck.
