What did the previous owners do for cooling? Not to say it is as good as AC but I have been in some southern homes without AC that were quite comfortable in the summer. They relied on shade trees, high mass building materials (brick, concrete, plaster walls), good whole house ventilation (attic fans), interior air movemement (ceiling fans) plus some ice tea or lemonade. The house is then vented at night and closed up in the morning. If your house has these characteristics, it might be better than you think. Just a window unit in the master for hot nights might be enough.