Why build a rig if you can buy ASIC units?
I don't think it's worth mining with GPU by checking calculators it still not worth mining unless you have a free power source.

Bitmain still selling units like s19pro hydro it is around $3k below.

Optional contact OffordScott for 2nd hand units.
You can message him directly here https://offordscott.t.me/
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I don't have free energy, but I have a 40kw photovoltaic system, so it's cheap