The 'ding ding' here is: Consult with your local experts, do what you can afford to do well, and know where your limits are before you hit them.
A bunch of fallacious stuff gets thrown around every time this comes up, like "you must have 24-inch raised floors", or "you must be on a 2nd or higher story of a building" ... anything that says 'must' is probably advice you can safely ignore.
Honest to god, I've seen some dumb stuff in my time. There's a department at my employer whose server admins (we are in a federated/distributed it environment at a large campus where many groups run their own small machine rooms) are known for letting their orange lights (dell kit) blink for months before addressing hardware issues. The main campus machine room once got hot enough that the flooring tiles warped -- without the ops center even knowing until a vendor-managed piece of equipment managed to call the vendor for help, and the vendor rang the ops center to ask what the hell was happening. (I think it peaked at about 125 degrees F.) There are so many single points of failure that I know of that I would probably win any sysadmin ePeen match with a new high score. Yes, it's terrible ... but, like most things related to the internet, it works despite breaking every rule known to man.
Back on the other hand, I've seen some gifted uses of limited resources. One that comes to mind is cooling. It's difficult to get sufficient cooling in a normal space on campus at a decent price without doing some serious improvements to the building's infrastructure. Since some of our buildings are historic, that's not likely to happen. One excellent use of limited cooling power was to vent all hot air to the outside using enclosed racks with APC-brand fan-back enclosures. The entire server "room" (four racks) was sufficiently cooled by a pair of portable units... but (most importantly) all heated air was immediately removed from the building and vented to outside.
Basic rules: Have enough electricity, a decent connection that will support your peak traffic, and enough cooling capacity to keep the servers from reaching thermal shutdown. After that, anything you can put together is just gravy.