If you're only virtualizing one server on that home computer, then you don't need much more RAM or CPU than an equivalent physical server would require. The biggest issue is that the system that runs the virtual machines itself requires CPU and RAM. The least resource-intensive solution is probably something like the free VMware vSphere Hypervisor.

This product gets installed on the physical computer, you then interact with it via an admin console which helps you get VMs running on it.