Is this for servers or comms equipment? The racks for both are significantly different.
There's a constant stream of surplus racks on eBay. Often for a few hundred bucks, sometimes pretty much free. If your equipment has its own rails, this is the best option. You can also use shelves, but they don't look as nice. Short and light equipment can just bolt to the front row of holes.
One thing to factor in though is that, with the exception of the much shallower comms-style racks/cabinets, racks are physically large, and will dominate almost any room they're put in.