Given the following scenario what would be the best set up?

The company is somehow connected to headquarters located interstate, but how would the 2 buildings be connected to headquarters? Would the HQ have one leased line to connect the 2 branch buildings?
A company is planning to open a new branch office interstate. They have office space in two different buildings. The first building (Building A) has one floor of 10 employees. Building A will have a conference room with support for wireless network access and videoconferencing and a file/print server. Second building (Building B) is located approximately 5 km. from first building. There is line of sight between the two buildings. Administrative staff (8 employees) will occupy one floor of second building and IT & customer support staff (10 employees) will occupy another floor in this building. Building B will have a file/print server, backup server. Company ISP1 will be used as an ISP to provide broadband ADSL access to the Internet. A VPN will be set up for remote access to the network.

How would the two buildings connect to headquarters interstate? And what would be the best option for connecting the 2 buildings to each other?

site-to-site VPN is definately the way to go, and if you know your stuff, not that hard to set up. And it gives you scalability, which is always a good thing.

VPN in general has two parts. There is the 'well protected' internal network and a less trustworthy external network.

The internal network is your Intranet. The external network is usually the internet.

A firewall usually divides the internal and external networks.

For your setup, there would be 3 firewalls, one at each site. They would all be configured as part of the same VPN.

here's an example. Say your internal 'secure' network are islands in the ocean. the water is the internet. boats are packets/traffic. A leased line is like building a bridge between the islands. It's still visible to other boats and is expensive to make (distance fees).

A VPN is like a submarine, undetectable by any boat or other submarine. Plus, it's easy to add more and more submarines to your 'fleet'.

So basically, a VPN establishes an authenticated connection over the internt. Only the firewalls will be able to de-encrypt the information because they're all 'in the know'.

Sounds about right now just what is the question?

There is a lot of unused fiberoptic cable layed before the .dot crash. Check at your county or city planning department and see if any is in the grid close to your two buildings. You might be able to pick up a lease for almost nothing.

Within the buildings a secure wireless system allows for the greatest flexibilty without significant infrastruce expentitures.

The best answer I can give you is site-to-site VPN connections between the two buildings, and site-to-site VPN from each building to HQ. I am familiar with the SonicWALL line of firewalls and know they can do the job, although they are expensive. Once correctly configured, you could effectively set up a domain between the two buildings with the site-to-site VPN between them.

IMHO, I would not even attempt any type of wireless connection between the two buildings. I know there is special equipment available to do this but it would be expensive and messy, not to mention the reliability would be questionable at best.