Residential electrical is dangerous. Maybe you electrocute yourself. Maybe you cause a fire 5 years down the line. Maybe you cause a fire for the next owner because you didn't know to protect the wire with a metal plate so they drill into it.
Having said that, 2 4090s will run you aroud $5,000, not counting any of the surrounding system. At that cost point, hireing an electritian would not be that big of an expense relativly speaking.
Also, if you are at the point where you need to add a circut for power, you might need to seriously consider cooling, which could potentially be another side quest.
