I hereby anecdotal-ly verify this message to be true. Every small repair shop i have worked at has tons of old hardware, including some harder to find stuff, as well. all in all, this solution is one of the better ones i've seen (even though it does require spending money!)

Or cheat - take pictures of the BIOS screens and Photoshop the required key presses to get to each option. Learn what makes the bios BEEP, and make it beep if you get lost to figure out where you are. Timing is everything. Using this method you only need attach a keyboard if your boot fails. Jonadab made a good point about having the scripts beep (or play tones i suppose would work as well) - but if you manually assign an IP address to a network interface on your headless box, as long as the machine actually boots you shouldn't have a problem with getting in through SSH. Just remember that some file systems enjoy wasting time by checking themselves every X days or boots or whatever, and you'll save yourself some frustration. another thing to consider is replacing the motherboard for like $10 with one that has an on board video solution, and only dedicating 7-8 megs of system ram to it. That's how i run my "spare" servers, and i have a bunch of monitors with dual inputs to switch back and forth.