If looking at 2nd hand DR's what are their main problems to lookout for? Oldest model to look at and max kms?
DR 200 problems:
Rear swing arm pivot bush wear. Recognised by squeaky noise. Causes poor handling and instability (wobble). Replace bushes frequently with new OEM parts or once and for all with needle bearing conversion from xx xxx

Dragging clutch: Bike will struggle to shift down without blipping throttle and try to creep when in gear and clutch is pulled. Caused by rusted steel plates in the clutch from standing for a long time. ONLY fix replace clutch plates - friction and steel.
Flimsy front brake: It dates back to the early DR200 and the 1980's. Whilst probably adequate back then I would rate it "underwhelming" by today's standards. Probably no real concern for a beginner and on dirt it will in an emergency get help from the rear drum - which is surprisingly effective.
No fix available, besides using both brakes.
The rather lousy front brake features on the DR200 just like the CTX200 Bushlander and TW200

Besides the above (which IMHO is little) it's a nice solid little bike.
They came in three batches:
- 1985 - 1995 DR200 kick start
- 1996 - 1999 electric start cast iron sleeve engine. Various models for various markets. Djebel with large round headlight, carrier rack and round speedo; SE with small rectangular light and rectangular speedo
- 2000ff electric start SCEM sleeve engine. Both SE's and AGRI versions as discussed earlier. The AGRI has some desirable features such as the nice large headlight and some less desirable ones such as the cheap chrome plated steel rims and the garbage bin lid size mud flaps (which fortunately can be removed & discarded without much effort).
Pictures of the various DR200's and links to relevant threads there:
http://www.wilddog.za.net/forum/index.php?topic=132980.0BTW I know of a DR200 kick in running condition. It needs some work (see above) but it is fairly decent overall. R7,500