First of all, it's a great camera, those are great lenses, nice flash, and that is a heck of a deal! It almost sounds as if it's too good of a deal. If there is a way to do it, see if you can test the camera and see the pictures loaded on a computer. That way you can check for dirty/scratched CCD, focusing problems, etc. If you feel like being really thorough, you can use the "Clean" mode in the camera to expose the CCD and check for scratches that way. Just be careful.
Run the camera through its paces using every lens and the flash. Listen for any unusual noises. If the owner hasn't reset the photo count, you can check for the number of actuations by looking at the file name when you load it on the computer. DSLR's have a limited amount of actuations, although it is very high and being the XT model it probably still has plenty of life left.
Other than that, just go with your gut! Hopefully it works out for you. It's good that you have the opportunity to check it out.