Vista - Need help on hosting

Hi,

My company wants to host virtual networks for different customers. I have
read a lot of configuring hyper-v with or without DC, failover clustering,
virtual machines, storage etc. But my main concern is the beginning of it.

What do I need to make a start with my hosting solution for 2 customers?
- 2 physical domaincontrollers
- 2 physical hyper-v failover clustering servers. (on these servers I will
install all virtual machines for customers)

How about security? Do I need to place the isaserver as a virtual machine
on my hyper-v servers or do I need to place one isa on a physical server and
give each customer their own virtualized firewall?

So I have got many questions and don't know where to find the correct
information for making this beginning.

Hopefully someone can point me in the correct direction.

Thx in advance,

Ramon