[onewhippedpuppy]

Big time cheap for a 4S. The stuff I'm seeing upfront:

Front and rear bumper fit isn't good, and the paint appears to be mismatched.
Big chips up front
Right exhaust tip isn't clocked correctly
Aftermarket wheels are the wrong offset in the rear
Ride height looks funny
Stains and obvious scratches/wear inside
Small used car dealer - probable auction car
Tacky fender badges and turbo badge out back

My bet is accident damaged with questionable title history.

EDIT: had to run earlier, so a few more comments. I would run like hell from this car. It's being sold by a dealer, so there's a reason why it is so cheap. You will be damn lucky to find a 2002+ 996 C2 for $20k, I sold a clean 2002 last year with almost as many miles for way more than that. For the most part nice S models are close to or over $30k. You can get a really nice no-stories 996 for $20k, but it will be an earlier model (996.1).