The most important thing is to know who your clients are and what they are expecting to pay, dont expect to compete on price if you go out and build a top of the line datacenter, its best to know how much infrastructure costs your market is willing to bear. If you look at several of the lower priced colocations out there, they have the basics, but the higher proced colocations are generally in the high realestate areas and have massive generators, air conditioning, fiber carriers and power distribution system, and you will pay for that.