My advice is to spend a couple of weeks here reading threads. All the questions you are asking already have answers, and the experience you gain from mining is not easily transferred so easily in a single message to someone who doesn't appear to have mined before.
Good miners are able to read the "tea leaves"... seeing what other people are doing, experiment, and make your own plans. There is no magic formula, and while I applaud your ability to sink $30K into mining rigs, you are taking on a responsibility that you may not be ready for.
I suggest you start with one rig. Build it, tweak it, learn how it works, find the pain points, and then decide if you want to spend the rest.
What are your goals?
I would aim to run for 12 months at least with these cards mining Ethereum if possible, if PoS happens before, I'll have to move to another coin...
What are your expectations for capital expense recovery? (some people call it ROI erroneously)
Calculating the hardware cost, and electricity, I'd assume that the capital would be recover after 7 to 8 months, assuming that ETH prices stay the same. But I'm certainly not planning to sell it quickly.
What kind of expectations do your investors have?
I'm starting this on my own to be honest.
Where are you going to be setting up the rigs?
A flat with proper connection, security and AC, with proper ventilation.
Do they have appropriate power and ventilation?
So far I didn't have any problem with one rig, and there's enough space, I'm not sure about the power/electricity instalation, it's worth to take a look at this.
Do you have proper internet, networking and other infrastructure available?
Yes, that shouldn't be a problem, I believe.
Do you have any plans for expansion?
Certainly not... like I said before, I started with one, and it didn't go bad at all, so I'm willing to increase a bit more the bet. The worst thing that could happen, might be running out of coins to be mined with these GPUs, but I don't have any information to make me think it might happen any time soon...
Difficulty increases will decrease your earnings over time, and investing so much in RX 580s may not be the best use of capital. They are good for Ethhash and Cryptonight algorithm based coins, but are already a generation behind the latest AMD cards. There are hundreds of coins available to mine, some GPUs do better than others. I would suggest you diversify the GPU types you use so you can react quickly to the changing scenarios that are out there.
Hi Puwaha, and thanks a lot for your ideas! I've been mining ETH since 8 months already with the same hardware and without any problems. I'm aware about the Vega 56 and Vega 64, but prices are about twice here, compared with the Rx580 8GB, and the hashrate doesn't seems to change that much.
Also I thought about Nvidia 1070, as I know they have better performance in more mining algorithms, but the price is +30% compared to the Radeon once again...