@CharlesWorthing
There are calculators.
You need to look at the payback period.
The other issue is that Bitcoin Hardware was, I think, going obsolete pretty fast.
I might try for Monero. The payback period is worse but you should be able to use the hardware at least 2-4 times as long as they are still mining at H/s and the a $350 GPU can get up to 30 Mh/s stock.
You can get 3 GPUs and the rest of the hardware for less than $1500. Once you mine another $350 towards another card, you can make ~ $1400/year minus electricity which won't be as much to start.