I have a small house(1400sqft). I put a small window unit swamp cooler in the living room window. I keep the two smaller bedroom doors closed. Costs is $10 to $15 a month extra. 102F outside right now and 77F inside. I bought a solar power fan for the attic to vent air from the the roof eaves to the outside, but haven't installed it. House came new with central air, I just don't use it.

https://www.homedepot.com/p/Master-F...OLAR/100548465