Basically each system which accesses the network needs it's own address (router, PC, VM, ...). I can't tell you how your ISP distributes IP leases, i.e. if you can get one for the VM on the host's uplink port. However, if your VM's don't need to be directly accessed from the Internet or only a few ports are needed, you may consider NAT networking and configure port forwarding in the Virtual Network Editor.
André