Single internet connection to 2 PC'S

Definitely!

You will just need a router (Less than $100 with built in hardware firewall).

The IsP's connection enters the router and as many PC as there are ports can be attached to it.

A small, basic 4-port router should suffice in yoru case.

Here's a few to look at that are inexpensive and found almost everywhere.

http://www.linksys.com/products/product.asp?grid=34&scid=29&prid=142

You can add a wireless adapter, great for notbook computers, but you will need to add a PCI wireless adapter card for most desktops.

[quote]Can we use a single server (ISP) for our internet conection, we would like to use the 2 PC'S in parallel?[/quote]

Yes, as long as you get a router that knows how to do dial-up connections. These are a bit more expensive, but easy obtained:

SMC Barricade (SMC7008ABR)
http://www.newegg.com/app/ViewProductDesc.asp?description=33-129-009&depa=5

MultiTech RouteFinder
http://www.multitech.com/PRODUCTS/Families/SOHO_VPN/