The regular VMware vSphere Hypervisor is free, and works on most hardware. You could go used, or check delloutlet.com. (sub $1k) It doesn't need high specs at all. The reason I mention is that usually you end up needing other small services. Virtualizing allows you to have a single box and add VMs as needed. It's also easier to setup carp/failover later if the system grows and you need redundancy. Running an ISP is 24/7 so being able to have full console access, and confidently reboot services saves late night trips. It's been a while so am not familiar with the current hotspot products.