You'll need to buy the right miner at the right time, first off. Initially, a new miner that costs 2000 like the S9 might seem like a lot, but considering the fact that you've made a bit over 250 USD if you bought it and started mining immediately after receiving makes the cost a lot lower. Also, consider the fact that the S9 still costs around 2000 USD - it may be risky, but buying a miner just as it comes out is risky, but can work. 2000 is overpriced for an S9 imo, because profit just slows down more and more every day past the halving. If you're going to invest in miners, also have cheap electricity. People with "free" electricity are much better off than people without free electricity, because the cut from power costs is lower. I would say it's not too late to buy an S9 farm right now, but it is riskier than a week ago or a month ago.
There are just so many variables I still say you cannot group all in one category. Most people with "free" have a limit of a certain amount of electricity, also a lot tend to be apartment (there are a few that have at business) but I think majority are apartment's. So these need to make sure the can handle the heat/noise. And you can do it even with the loudest of miners at one point when doing reviews on miners I slept with them in room for a bit, but something to think of and some do things to make quieter.
I think it can be done with paying for electricity, I would not attempt at higher then 10 cent's as you can find hosting for it. The question is how long can you run a miner at that... it comes to speculation but I would guess some will mine to a point and sell and ROI. Others will cheap electricity will mine them into the ground and pull off ROI. There are lot's of way's to do it.
Also a HUGE thing that does not get mentioned much is if your buying in BTC or USD. If you buy a 2,000 USD machine in dollars then you just need to make over that 2,000 to have a return, a big upswing in BTC price can help a lot with this one. There is argument you could be better off of bought and held coins... but still ROI is ROI. Now say if you pay 3 BTC your end goal is to get more then 3 BTC. So I think what your purchasing with is a factor that should be mentioned more.