Here's another vote for holding off on the preamp. It's a big investment for someone just getting started, and I've never found I needed one for anything amplified (or even clearly audible acoustic). I don't see the point of getting a preamp and turning it down to zero when you can get the same power to the mics via a battery box for 1/3 the $$.
If your friend is lower-budget or impatient, the Sound Professionals BMC-2 binaurals are what I started with, and those recordings sound pretty good. (Get the clips and, if they're getting a lot of use, the 3-year warranty.) The Naiant X-X stereo mic for $69 also looks tasty, but a lot bigger.