If you decide this is what you want to do, then before you sign a contract with such a company, you need to decide a few things. Of course, setting a budget is always one of the first things you need to do because it is very easy to quickly go way over budget and then regret it as you have to take away things that sound wonderful and useful. If you go in with your budget in mind and that is almost the first thing you tell any prospective companies, then they can avoid going crazy with marvelous options that you just cannot afford. And keep in mind that the cheapest bid for your business may not be the best one for you. So often with computers and other technology aspects there are many things that go into creating value. If a company costs a little more for their design services but offer extras such as free system checks on a regular basis or perhaps the ability to come in and help you as you expand down the road, then such a company might actually be worth the extra cost.
You should probably have an idea of how many servers you will want to house and what the servers will be doing. If they are simply going to be backup storage, then the protection of the power grid around them may be much less vital than a server that provides medical interfaces with a series of clinics and hospitals where a server outage is simply unthinkable. That does not mean you have to make the final decision on size, brand, or number of servers, but you should know whether you will just be working within your own company or whether you will have clients counting on you.
You should also have an idea of who will be working with the system so that the company can structure the data center to work with the sole employee who will be in charge of the center or all 500 of your employees that need to understand how to work within it. You should also need to know whether you will have an IT staff of professionals working with your computer or whether it will just be amateurs who need to have very easy designs and instructions.
Once these decisions have been considered, then it is time to find a date center designing company that will give you exactly what you need.