Watch out for noises from the 2.4 engines on the LWB RWD models. They tend to eat the bore of number 1 cylinder if not maintained correctly. When I was @ Ford, they would not warranty a replacement or repair if the servicing had been overlooked, it is that specific.
Feel for any judder on the clutch when pulling away as the dual-mass flywheels can go, taking the clutch with them. Replacement is either a new clutch and flywheel dual-mass combo @ about £400, or retro-fitting an early-style clutch and flywheel (still not cheap).
Make sure every key works the ignition as if you use an unprogrammed key in the ignition, it wipes the lot as a security measure. Better to find out before you buy than after.
Remote controls for the locking can and do play up, but they are cheap to replace and can be programmed manually.
Also, there was a security modification on all these Transits where 2 L-shaped plates were rivetted to where the looms go to the rear doors. People were having the looms cut which meant that the back door could be opened and stuff nicked. It was retro-fitted on the next available service schedule. If they are not there, then either it ain't been to Ford for servicing, or the workers there were shoddy.