First thing you need to do is determine your cost of power in your area. This is the basic raw material direct cost that will determine profitability. Then consider the entire computer hardware cost as a "capital" purchase. Once that is done, you have to put a realistic lifespan on your hardware investment (let's say 12 months considering the difficulty levels of mining will increase forcing your equipment to be obsolete faster than a regular computer lifespan). Once you have these numbers, then you can determine the Mh/s you can generate with your rig, and what that is going to generate in terms of ETH. The price of ETH will fluctuate and if you need to pay your expenses with the ETH you generate, then your profit is what is left. Or your loss if you have a shortfall. That's it. Otherwise it is just the tech stuff to put that together and there are thousands of posts, videos, etc. to show you that. But just consider your costs before you embark on this journey.

In my case, I believe in the vision here and I don't care if I lose money - I want to contribute to the blockchain by mining and I want to generate new currency. I'm punting on what that will be worth for the future. But others may not be able to fund such a punt. So your mileage may vary.

Good luck. Oh and read my blog here: https://steemit.com/@beunconstrained There are important articles there that will affect your journey.