Attic fans are designed to pull the hot air out of the attic and get the air circulating. If you get a attic fan make sure that is temperature controlled. When it is hot it will kick in and when the temperature drops it will not run. If you get a manual run attic fan you will have to turn it off and on.
The fan that really cools you house is a whole house fan. It pulls the hot air out of you house and puts it in the attic and the attic fan shoots it back outside. It really make the air circulate in your house.
Make sure to get an union electrician the insured and bonded if needed in your city. Don't forget to get the contract and warranty in writing.