First of all, if anyone still mining Bitcoin must be a hobbyist enthusiast or just plain don’t know how to calculate the profitability. Even for this new Bitcoin minger so call BTC Garden 310GH/s Bitcoin miner for $330, it will takes you a long time to get your ROI back. My estimate would be more than 6 months, factoring in the electricity cost, the difficulty level rise, and price of Bitcoin isn’t going anywhere much up and down at $600
If you want a quick calculation, you can plug it into website like coinwarz.com and see. For this device. 310GH/s, 325watts, 13 cent per kilowatts. Price of Bitcoin $630, you will be making $4.83 a day, multiply that by 30 = $144 a month IF and I IF a big IF, the price of bitcoin doesn’t go down stays at $630, no it’s ain’t gonna go up, and the difficulty doesn’t change. But we all know the difficulty changes every 7 days or less, and when it changes, it could double or double depend on the hash rate, and we also know that, there are a lot of Bitcoin mining hardware manufacturer out there hashing away before selling the hardware to you which pushes the difficulty of mining skyrocket.
Bottom line, if you have that $330, it’s better to go and buy Bitcoin directly from many Exchange such as Bitstamp and Coinbase.Then always store it on an offline Bitcoin wallet. Chances are in 5-10 years the value of Bitcoin will be a lot higher than it is today.
If you want to continue mining because it’s fun, maybe mine with one power efficiency unit, just for giggle, but for sure mining has been obsolete for individuals to even small size mid size mining farm operations. Bitcoin mining are now just for commercial. People whom have money to invest in a datacenter, cheap electricity, these are the folks that will profit.
Don’t try to diversified either. Just buy Bitcoin directly. If you buy the miner hardware, it would take you a long time to get the same quantity of Bitcoin you could have today by buying Bitcoin directly!