There is no way anyone can ever tell you the ROI / profits you are likely to see. Anyone who tells you they can, is a liar.

I use profit calculating websites like whattomine.com and https://www.coinwarz.com/cryptocurrency and https://www.nicehash.com/profitability-calculator

Those websites can give you a rough idea of what you are likely to earn AT THAT VERY MOMENT. However, the next day, it can completely change. And it might be really profitable for months so you keep all your coins, and then the price plummets and your coins aren't worth much anymore, equally, you could sell them regularly and then the price sky rockets. It's all about personal preference and risk assessment, just like a normal stock market.

The coin you mine would depend on what cards you buy. Ethereum is a strong currency (second only to Bitcoin) with a big following etc. but that makes it difficult to earn many coins. A lot of people mine smaller coins and trade them for ethereum etc.

Personally, I am mining ZCash because I have older 280X cards that aren't very good at mining Ethereum, but my new rigs will likely mine Ethereum.

Ethereum would be profitable if you have free electricity.

I find the main issue of hosting rigs is supplying them with power and heat.

You have to make sure that there is enough power coming from the breaker box etc. and need to know detailed information about your electrical layout. Many people move into an apartment with electricity included in the rent and want to mine, mine, mine, but don't factor in having to mess with the electrics, insurances problems, and the heat!

The heat for me is why I stopped mining at home. Granted I have rigs full of older, less efficient cards, but the I wasn't able to expel the heat effectively enough and it was quite miserable living with the rigs in the summer.

Just some things to think about.