How much you make can be directly correlated to the investment which you put in. Never think about how much you can make in USD (or whatever your local currency is), rather about how many coins you can mine in one month. I say this because the market can flop or fly at any time. Ethereum, for example, may be worth $380 today, but only a month prior, they were under $20. This can turn $1100 per month into $60, or vise versa.
If you have one computer running your old RX 470 4GB card, you might only earn 0.126 ETH per week. Again, at current pricing that might be $48, but at $20/ETH, that’s only $2.52.
The easiest tool you can use for rough estimates is WhatToMine. If you have a supported card, enter the number of cards and your electricity costs. For me, this number has proven to be ~19% higher than my actual monthly return, though your results may vary.
More advance users will have far better accuracy using MyCryptoBuddy which accounts for dynamic difficulty changes.