For a simple MSCS clustering solution with low hardware requirements, you might choose to have one standby host.

Set up your system to have a virtual machine corresponding to each physical machine on the standby host, and create clusters, one each for each physical machine and its corresponding virtual machine. In case of hardware failure in one of the physical machines, the virtual machine on the standby host can take over for that physical host.

The following figure shows a standby host using three virtual machines on a single physical machine. Each virtual machine is running clustering software.

Clustering Physical and Virtual Machines
Clustering physical and virtual machines