Peripheral

It is not as simple as you appear to think it is.

Each "client" would need to be a terminal. You need some additional hardware besides just the monitor and keyboard.

Then, the "PC" would work best if you used a server rather than a normal PC.

The simpler setup would be a single PC or server acting as a gateway with each client being a networked PC.

With a server and a managed switch, you can then control what access each client PC has.

As far as how to set this all up, my best recommendation would be to contact some local IT support firms or consultants and have them help you set this all up.

Chas

You might want to check this out. I've seen it implemented in a school environment before. 1 server type PC with multiple stations of LCD/Kbd/Mouse only
http://www.ncomputing.com/

Not sure about the billing software. Sounds like a cybercafe. I've used this before. http://www.cybercafepro.com/

This is probably possible with Linux and separate X servers. You'd need a motherboard with a ton of PCI Express slots for all the video cards. I don't know if 15 would even physically be an option.

Getting it working would be much more of a "because I can" benefit than truly being the best solution. I agree with nocjock. There is quite a bit of software out there made for Internet Cafes. They can completely replace the Windows shell, handle individual user logins with back-end billing and time limits... all the stuff that you're going to have to enforce to make it a profitable venture.

You're also going to want to look into imaging so you can restore the OS to a known-good point after the inevitable malware/virus attack. Microsoft's free SteadyState is actually a good, fairly simple (and free) product for this. You can revert ALL changes to the disk on reboot (unless you log in as Administrator). This has worked surprisingly well on some hotel public-access PCs that I've managed in the past. Over a year with NO problems. I think it only works with XP, and MS is discontinuing it, so download it quickly. (Figures..)

Read more here and also you can test out the software:

http://international.ibik-soft.com/