Demand is way to weak to make this profitable. If you still want to compete you need extremely fast (overcloked) single core speed and almost no power consumption at idle. AMD and Intel is trying but so far it's not enough.
Here in Latvia we get like 0,16$/kwh tariff.
And if my pc systems are able to get say 10$/month
Then we should compute what is break even point for 10$ : 10/0,16= 62,5kwh and that is about 86 Watts 24/7.
Basically if you can make 10$/moth and use less than 86Watts on avarage - you are making something.
Sure, if go bit more fraudulent ways when you get electricity for free you could get some income but since demand isn't there you be making few bucks a month if you lucky.
There are much better ways how you can make money passively using your pc resources. I do sell my pc resources to cloud but I doing that because I like who whole system but not for profit.