Notchy headsets and play in the track-rod ends are normal wear and tear (ICE can supply the parts, but factor them in if they need doing).
Similarly chain tubes (especially that rubbery bit that facilitates the fold, which seems quite vulnerable to damage when the trike's in the folded state).
Take the seat off and make sure there isn't damage to the seat frame and/or the lower thingy it rests on (if the rear end isn't straight in the cruciform, the seat takes the stress), and have a look at the main fold hinge while you're there (I don't think these are a particular problem, but it could be expensive if it needs replacing).
Check the underside of the cruciform for damage from scraping on kerbs or whatever.
Fabric seat, obviously.
I think beyond that it's normal bicycle stuff. Oh, if it's got a 20" rear wheel with a Capreo hub (derailleur gears that go down to a 9t sprocket), I think those have been discontinued. Not an insurmountable problem.