Mary,
Stan just gave some great advice. If you go used, I think a good way to "know" the car is to buy a car that has a history on this forum. You can do a little archive research and get a feel for the owner, the cars modifications, and etc. You can also p-mail some folks on this forum that have a strong understanding of VW mechanicals. Stan would be one I'd go to (and have).
I just sold a very nice 3+ year old 30,000 mile VS that had many add ons, a built 1776, etc. to someone who knew the car. It wasn't too bad of a hit considering the fun meter was pegged the entire time I owned it. Still, the new owner got a bargain.
Another thought. You are close enough to LA that I would consider keeping your search for E-Bay and other net sources to the SoCal and AZ area. Any LA car would be easy to have checked out by a number of great shops, and if it is a VS or JPS, you could take it to them for a look over (and history). The added benefit of a local car (AZ/SoCal) would be the cheaper cost of getting it home.
I think some of the used IMs you are seeing for sale may seem depreciated because of their vintage... a pan based Roadster or Speedster is going to be sold at a lower cost. That doesn't mean they aren't great buys though. There are several Pan based IM Speedsters on here that are awesome cars. Rick Davis has a solid and great looking one. There are other's, I think Glen has a pretty neat one from what I can tell by the pics and the mods he has made to make it more authentic appearing. But, to get a used IM Speedster on the custom frame is pretty difficult. It may be a couple of years before you see more than 1 a year for sale. It's only been 3-4 (?) years since IM put out the newer Speedsters. One of the early (custom framed) IM Speedsters sold a few months ago for a great price.. I think it was around 26G.. a bargain for the car. The used Roadster/Vert D market is a little more active, but only because the custom framed ones have been around for a longer period. They make excellent buys if the Mechanicals are checked out. There have been three or four member's 'Vert Ds that sold on this forum or e-bay in the past two years that were very good cars.
Good Luck!
Jim