My English knowledge is average so please sorry for grammatical mistakes. Thank you
Proof that if you buy RIG just to mine ETH is not a good idea: https://www.ethnews.com/ethereum-community-vote-on-miner-rewards
There are a lot of threads where people are saying that the moment to start mining is lost...But people are still begin mining!
First of all you do not understand what means difficulty and what means return of investment.
I begin mining one year ago... And it was already to late for me to get in. Why? Because the amount of Ether produced in all this time by me is lower, than if with the same amount of money I invested in production, I would buy directly Ether's! Yes! And I started 1 year ago. Difficulty grew up very fast and amount produced every day become lower and lower! I don't tell you problems with heat in the summer and freezing Rig's ... So if I would buy Ethers at 10$ (at this price I can buy exactly amount of Ether I produced in one Year) one year ago I would sell now at 4 times profit! But there was moments when Ether fall down to 6-7$ (At this price I would buy much more Ethers than I produced in 1 year) which I would sell at 7-8 times profit! Or I would sell now just an amount to recover investment and wait for Ether to go to the moon!
Big Idea is that now is the same. Just make a calculation. With a computer with 5 rx480's you will produce about 0.27 per day, that's 8 Ether's/month (if your computer will work 100% of time). But this you will produce in first month, in next months amount will be lower and lower! In just couple of months amount of Ether produced can be 4 Ether's/month. For Example as evidence of that in November-December 2016 you would produce 150-200 % more than know.... You can check the difficulty graph for evidence... Also there is POS coming...which can happen this year! So you will never return your investment and will end up with less ether than you thought you will have.
If your investment is 1500$, for 1 Rig, you can produce approximately 35-36 Ether's in next 6 months and less than that in next 6 months ( if POS will not come ). Lets say 60-65 for first year (PLEASE NOTE THAT YOU WILL MAKE THIS IF YOUR COMPUTER WILL NEVER SHUTDOWN). You will pay electricity about 80-110 $/month depend of the prices... which is about 1000$ per Year. So your investment is 2500$ for POSSIBLY 60-65 Ether's! And don't dream that something will happen and you will have more
That's the maximum, you could end up with less than that. If you divide 2500$ to 60 ETH = 41$/ETH.
So at the today prices you can buy directly the same amount of Ether and wait 1 Year for the price to go up! Or you can wait for the price to go down to 20-30$ and buy more Ether's and when the price is high enough for you to sell. And if you think you can sell the Rig after a year, maximum you will get for you Rig is 50 % of 1500$ and it will take time to sell.
Other problems are that if you have working Rig at home that means a lot of heat in the summer, noise and safety problem ( when you go in a vacation or somewhere for the weekend you need to ask somebody to be close to your house, in the event your Rig Freeze and you don't know if there is a fire or what is the problem..)
Conclusion make for yourself, i just posted something which is real world calculations...