It was a difficult task until a few years ago. With the appearance and accelerated advance fabricated by the Internet, this has become child's play. One can get the best accessible online deals and the features, prices and other aspects of the choicest brands are compared instantaneously.
Depending where you live, you may be able to hunt for some commercial real estate building that may have unused data center space. search for keywords like, raised floor, generators, raised tiles. Many time's the company looking to lease the property is looking to demo the equipment anyways. that's how you beat the refurbished companies.
This sounds like a pretty good idea and seems like something that would be very feasible. I think you could really get some good prices while still having equipment that will be very reliable.
Just a quick word of advice, be careful in choosing used equipment. With knowing the equipment is used you expect that some things will be "not the best" but make sure you buy from a company with a good reputation because I have saw so many get burned and spend a good amount of nothing and receive junk in return.
I couldn't count how many times I went to a customer's business where they bought a bunch of old server parts and asked me to put it together and run their business with it. A bit of research will save you a hell of a lot of time and money.