They're asking $3,999.00 with 18,000 miles. It's that Plasma Blue.
Pretty 'average' price for a 900C.
Make sure it fits well, make sure to sit on it!
'06 and '07 models are notorious for stator failures. Make sure there's no whirring/whining sound coming from the left of the engine, make sure charging voltage is good.
Check the usual stuff. Look for scuffs or things that might indicate it was dropped, look for signs of unusual wear, etc. May not be deal breakers but certainly might be reasons to tell the dealer they are gonna have to come down a bit. $4k is a decent price for one in very good condition, not one that's scratched!
When I look at used bikes I also make a habit of checking under the seat and taking a look at the wiring. No clue what the PO had done and maybe the PO cut and electrical-taped the heck out of the wiring to install their portable espresso machine or whatever. If the wiring looks like a mess, then you probably don't want it, lest you be posting threads on here chasing electrical gremlins!
Other'n that, show us some pics! You'll love the 900!