That depends on the budget.
I would purchase one or two older Dell or HP servers from EBay, with as much RAM in them as possible. I think you could get two Gen2 or Gen3 Dell 1950s for between $500 - $700 total, with 16 GB of RAM each. Those would work. I have used them for dev environments in the past. Shove some large, cheap SATA drives in them if they don't already come with drives, and you'll be all set.