Would you invest 2000$ on a 140MH rig? Forget what the GPUs are I'm talking about MH wise, is this a good investment or a bad one?
You are asking the wrong question.
If you are buying RTX 3060 and RTX 3080, then this is a very good offer. If you are offered to buy a 5xR9 390 five-year mining farm, then this is a bad offer.
You will recoup your investment if the farm works perfectly, so which equipment you buy is very important.
Can 5x R9 390 gives 140M? I don't think that's possible, for OP I think 🤔 it's all about the hashing power (140MH) and not how many watts the GPU will takes or how old the cards are, it shows that very electricity is available somehow, my advice is to keep things tidy it's better to go for bigger cards unless price are too much, rx580 and 1660 super are great options