Normally you can see if there is an AC unit outside. Often times it will be listed in the listing at http://ohiorental.info. But it may not always be listed there.
If you see an air-conditioning unit at a property and air-conditioning is important to you in renting this unit make sure you verify that the unit is working and that the landlord intends to either repair and/or service the unit.
There are landlords that choose after an air-conditioning unit breaks down not to remove it and not to replace it.
In Northeastern Ohio the law does not define air-conditioning as a feature that is required for a home to be habitable..