Hey gang,
If my start up budget were TOTALLY limited, I'd spend the money on a high-quality network switch and/or wireless router, and start peer to peer. You can ADD a server later.. to upgrade a low-end switch or router you have to REPLACE what you bought - which means buying it twice.
That being said, our MAIN PRODUCTION server here I bought on e-bay. I replaced the hard drives before deploying it, as I'm nervous about used hard drives. The server, FOUR drives, and assorted goodies was about $500, for a dual processor RAID server with two 10/100/1GB network NIC's. Not shabby. Our e-mail and web server was $65. That's right - sixty-five bucks! It's been running without a hitch now for two years. Shop SMART, and your money goes farther.
Let me know if I can help.
Regards,
V.