however this is not the problem with miners today. the ASIC cost is.
at todays $2100 pricetag plus $120 for a PSU that is going to be the major lump you have to recoup.
so knowing its going to be an initial outlay of $2760,
also current maths of todays estimated mining income and considering the fortnightly drop income due to difficulty adjustments. you will expect to get ~1.2btc after 6 months.
no one would in their right mind pay $2760 for 1.2btc..
you would be far better off just buying 2.5btc now and hoarding it.
the reason that people do mine is because they get the rigs 'at cost' (estimated at under $400) mostly though its the asic manufacturers that are the ones in profit to sustain mining.
this is simply because for every rig they sell at retail($2100) they can make upto 5 rigs.
what they (if smart) would do is make 3 rigs. give 1 rig to the customer. put 2 rigs online and have $600 spare to go towards paying the electric, meaning thanks to their customers, asic manufacturers get 2 rigs for free and cash to cover electric for free. thus any bitcoin they get, is 100% profit
unless you can get a rig dirty cheap, at lets say a quarter of the retail price forget it. but thats my evaluation based on bitcoin mining
others will suggest altcoin mining.. but thats hit and miss based on timing of mining the right coin at the right time and selling it at the right time of the pump.. before you hit the dump