i would pass on that car. For $27k you should be able to find a similar car with similar miles without the accident.
Without seeing photos of the accident you are really taking their word on the extent of the damage and repairs performed.
If it is an 09, does it have any warranty left? if so, you could possibly negotiate the price down and get an extended warranty with bmw if you are really set on the car.
MY Build Log
08 AW 135i | Cobb | ETS FMIC | ER CP w/ Tial Bov | AR Catted Downpipes | Berk Mids | Meisterschaft GT SUS 1M |M3 Control Arms | M3 Sways | M3 Rear Subframe Bushings | Wavetrac LSD | AST 4200 DA Coilovers | HRE R43 | Hankook R-S3 |Full BMW Performance Interior | Revozport 1M Raze Aero Package in Satin Carbon |1M Body Conversion|