The thing is no one really knows what mining will be like 3-6 months down the road. Card prices are sky high right now and AMD is coming out with Vega cards in August. Ethereum could go PoS by end of the year etc.. Don't expect to turn a profit until at least 4-5 months down the road.
Like I said, if I get more than 50% of my return back within 12 months, I'm calling it a success of sorts. Nvidia are also inching closer to their 20 series cards, which I think will have a big effect on the current 10 series cards. My plan on that front is to hold out until early next year when I would be looking to expand. Right now, my aim is to have a setup where over the next 9-12 months, I'd get 50% or more of my initial investment back. I've checked every mining calculator I can find, and with 580s, it seems possible.