Managing Multiple Clients under one Sonicwall

We're looking at beginning to offer colocation services to our clients utilizing datacenter space that we're currently renting.

The one problem we're running into , is that we want our clients to be able to easily establish site-to-site VPNs from their office to the datacenter for secure access to the items they have in our facility.

We had originally considered simply deploying a new sonicwall inside the datacenter for each client, but we quickly realized that this could be very limiting for scalability and price if everytime a new client was deployed, we had to also put in another firewall at our facility.

What we were wondering, is if it would be possible to purchase ONE sonicwall (even if it was a bigger more expensive Sonicwall) and configure it to manage multiple networks with multiple different VPN policies.

So the idea would be that I could have 3 clients, with 3 different servers, on 3 different "networks" in my facility, and that all of them maintain a VPN connection from their office into the datacenter, but each of them be limited to only accessing an internal network configured for their company. This way, we can offer them an easy way to maintain a VPN connection to their equipment in our datacenter without them having to incurr the added cost and space of another firewall in the facility.

Any advice on how this could be done or what type of Sonicwall Firewall would be required?