2000 323i's still sell easily for over 20k at dealerships as CPO's. You can get them under 20k from private sellers. You won't find a non-wrecked 2000 anything BMW for 10k, period.
If it rides smooth, and there are no other big issues (get a reputable euro or bmw only shop to check it out) then I'd say it's a pretty good deal. BMW engines get better with age if maintained correctly.
MrM3 said it best. As long as you don't have any big physical blemishes, no overly worn suspension parts, and the engine is sound.. it's a great car for the price. You might end up fixing some things that wear out sooner than other 2000 owners might, but that's the downside of the milage.
Lastly, if this guy has done you right with 2 cars previously, and you think he's honest, then that really is the cherry on top I think.
<img src='http://188.8.131.52/coDataImages/p/Groups/12/12267/folders/124915/1454131newsig.jpg' border='0' alt='user posted image' />
<a href='http://seboc.com' target='_blank'><span style='font-size:8pt;line-height:100%'><span style='color
- Southeastern BMW Owners Club</span></span></span></a>