For single users, having a virtual hosting local setup is great! It is even part of the process when working with other users, but having a hardware development ESXI box can be an awesome thing for several reasons.

• 1) It's VERY simple to spin up a new virtual machine, giving you:
1. 'Dedicated' resources (RAM, STORAGE, CPU)
2. Easy to show 'custom' dev sites to clients (dev.clientdomain.com)
3. Easy to export to a production ESXI server
• 2) Integrated monitoring over resource usage.

So, what server to buy?

There are many used servers that are relatively cheap. But wait, aren't used servers rather dangerous to use (near end of life)? The thing with servers is, Hard Drives will (generally) go down long before the non-moving components in the server such as the motherboard, ram, power supply, etc. so if you get new drives, you could easily get years out of a used server (though I would be wary using a used server for production. It can be great, but you must be careful or your sites will possibly go down if your server goes bad.