Many people will have opinions on this, including me. :-) From my own experience, reliable VPS providers that are less expensive than AWS would be Linode and Vultr. Vultr natively supports iPXE if that is something you want to learn as well. Both have pay-as-you-go plans, meaning if you want to destroy the VM's after 5 days, then you only pay for 5 days. Both have very fast VM's.