I have a lot of people that want to invest in mining rigs in my city, over 20 people.
I am looking for someone that has lots of experience in mining, that can help me with the parts and everything.
Would this also be profitable for the clients? Since ETH will be turning to POS and mining might not be as profitable.
I'm sorry but based on the nature of your question the only sensible thing to advice is to not do it. Seems like you have no idea what it takes. Basically the added value you have for your customers is that you have a bitcointalkaccount and they don't. It just boils down to "gimme your money, I'll google all this shit for while you pay all the learning money and also pay for all the trial and error. That is not a solid business plan.
PS: This might sound harsh but, coming from an above average experienced businessman, it's the truth.