You've had some good advice here.
Remember that you're buying a share in the assets and liabilities of the syndicate, not just a share of the aeroplane.
Damp rot can be an issue as described; also wing trailing edges and lower firewall.
Often a recover is the only way to fix it. With modern fabrics they usually last 20+ years and only re-covered to address issues in the underlying woodwork.
The brakes on 100 and 200 series Jodels are tricky to set up with their unusual arrangement for differential braking at the end of rudder travel combined with a single hand brake operating on both wheels. Check that's working as intended.
Most o-200s have had their original sprag clutch starters replaced with modern lightweight types. The old type are notorious for requiring maintenance and repair and occasionally breaking with debris in inaccessible places.
All that aside; it's a very capable aircraft on an O-200. Easy control on the ground, good forward view, but don't think of it as a 4-seater unless your back seaters are very light and young.