First, WELCOME to SitePoint!
Next, this is NOT advised because:
- It would be against your ISP's T&C
- It would require that you monitor your connections 7/24/365¼
- It would subject your PC to round-the-clock hack attacks
- Host's sysadmins know how to maintain a server (you've already said that you do not)
It's not worth the little savings you may gain by opening yourself to these problems.
On the other hand, I've long used a PC to test all my code before uploading to my hosts' servers. Kevin Yank's book can help you set that up quickly.