Flagster,
If you are considering new, I would highly recommend calling Dave aka "The Sprinter Guy." You can google him...he's based in Austin TX and has the best pricing on new custom order Sprinters(I have no affiliation with him, other than researching Sprinters for over a year). Also, as Mike mentioned, the newer NCV3 vans are highly complex and often have problems, even new. My brand new 2012 144" Van had EGR problems that showed up when the van was practically new. Mike also mentioned ordering certain options...I would second this. Things like factory tinted windows, the hitch, Xenon lights, factory swivel seats(yes, you CAN order this from the factory) etc will be cheaper to order now than add later.
If I were you, I'd look for a low mileage 2005 or 2006 Passenger van. You get the nice 5 cylinder TD that will run for a half million miles. Should be able to find one for $20k or so depending on condition. Check out Sprinter Source for all things Sprinter...
f.