My lab is small and cheap, but it's enough for testing a few technologies.
As a hypervisor I decided to use Intel NUC 5th generation with Intel Core i5-5300U, 8 Gb RAM and SSD. The NUC5i5MYHE is a corporate model without WiFi, Bluetooth and IR, but with vPro (remote control like HP iLO) and good frequency.
As a storage I use NAS D-Link DNS-325 with two 2 Tb SATA disks. On NFS share I place VMs without high IO requirements (like AD).
Total cost is about 650$.
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