It's easy to set up a single Bitcoin mining device and run it. Scaling to something that can make a significant amount of money is a different story, however. To make a profit, one needs reliable revenue and low costs. This means low costs for all aspects of the operation:

Equipment
Electricity
Cooling
Infrastructure
Business Management
Operations and Maintenance

Bitmain Tech Antminer S9

Bitcoin mining hardware is the first and most important part of the operation. If you can't get good equipment at a good price, you might as well stop right there. At this point in time, the best equipment to buy is the Bitmain Antminer S9. You should be able to generate about 0.5 Bitcoin per month (as of July 2016, post-halvening).

The Bitmain Antminer S7 is a good choice to learn about mining. Depending on your electricity prices, it might be profitable for you to operate it.