The bottom arms and figure of 8 links on the front suspension are c£500 to do in parts alone.. bit of a pain, but manageable if you're ok with tools.
If its an ST205 then I'm pretty sure it'll be a 1994> mate.. and the engines are WAY more reliable than the ST185 engines were, they've got a metal headgasket rather than the shite fitted to the 185. Plus, they run a chargecooler rather than a small top mounted intercooler on the 185.
Don't be swayed towards a WRC over a Non-WRC version... the changes to homologate the car were bullshit, nothing worked (even if activated, they're bollox) and the only differences visually are a small bonnet spoiler and the rear spoiler raiser blocks.
Cambelt/Water Pump service can be costly, but needs to be done as per schedule.
Radiators are known to pop, specially if you raise the boost, a sign for this is the top (visible) part going milky brown colour.. it should be a dark grey.
They hit fuel cut at 1.2bar of boost and have limited boost available in 1st (and 2nd think) gear so dont feel electric as standard.. more of a progressive surge than a kick in the guts when you floor it. The engine won't thank you for fitting a fuel cut defender, so don't be tempted to bang one on and wind up the boost... its likely to do a lot more harm than good.
If you fit a boost controller then you'll have to bypass this valve that limits the boost, meaning you get c1.1bar (or whatever you set it to) in every gear.. that certainly gets them off the line quickly, a friend ran a 1.6 60ft time on an almost standard ST205 with just an electronic boost controller set at c1.15bar boost on road tyres a few years back.
They're heavy fuckers, so don't expect them to enjoy being chucked around the back roads like an Impreza or EVO would do.. specially if still standard, because at this age/mileage then its likely to be a little tired.
Quite a while ago now, but here are pics of both of mine... I owned the White one twice it was so good.
Cheers,
Grant