I recently bought a Zoom MRS4 off ebay for £50 secondhand. This is a portable 4 track recorder, very good for overdubbing (a la Mike Oldfield) which I'm having much fun with at the moment. You can lay down a guitar track, then sing to it, then add harmonies etc.

I also needed some mics (2 ideally as it had two mic inputs) so bought a cheap one off the net for £16 (A KAM KDM500) which seems ok to me (Any comments on this anyone?) plus another unbranded one for just a few quid which also seems to work ok. Then I found I needed a mic stand to position them properly. All in though I've spent less than £100 and got what I think is a reasonable setup for home recording/editing. Admittedly I wanted to both play instruments and sing, not just acapella but I dont't think that makes much difference.

cheers
Ged