3. LOOK VERY CLOSELY AT CHEAP RACKS
A good rack will last you 10 years. A bad rack will last you 20 years and piss you off every time you go near it. Imagine mounting a full-depth POE switch to the front rail of a rack, then seeing that the back of the switch is about 2RU lower than the front, because the front vertical rail has bent under the weight. That's what happens when they make the vertical rails out of 1mm low tensile steel, not 2mm high tensile steel. Or, imagine having a server or router that has decided to put a RJ45 port on the front (usually an iLo port) and you find you have to either leave a whole RU free above the server to run the cat-5 cable back. Welcome to the joys of an APC rack, where the vertical rails are moulded to the edge of the rack.
What APC racks are you referring to? Even the cheapest NetShelter SX allows all vertical rails to be moved and they're thicker than 1mm. Or we have different definitions of cheap.