Actually, it doesn't require that major of an investment... I just finished a recording project where we used 7 drum mics into an SM162 mixer.
You can pull it off if you're willing to spring for a multi-channel sound card for your computer (I used an M-Audio 1010LT) and multi-track recording software (I used Sonar 2.2, but there are cheaper alternatives).
One thought, though, on the "less is more" theory... you may find that you can get some pretty good drum recordings by using less mics, thus requiring less channels. Start with a
bass drum mic and 2 overheads, and add other mics only as necessary. You may be surprised how good the results turn out with a little creativity in mic placement.
--B