What is a one-sentence summary of the following article?
A central air conditioner is the most expensive and difficult-to-install option, but it can cool your entire home. A central air unit will cost you between $3,000 and $7,000. On top of this, you’ll also have to spend money on a pre-installation evaluation of your home, any necessary modification or installation of ductwork, and the actual installation of the unit. During this evaluation, a qualified HVAC professional will check your home’s ductwork to make sure it can handle the airflow of a modern air conditioner. They will also look for places where air leaks from your home, and determine the cooling capacity that is needed to properly cool your home. Call or visit a local trade organization for a list of qualified evaluators. Ask friends and neighbors for contractor referrals. You can also ask for a list of contractors from a local trade organization.  Ask potential contractors for a list of customer references who can testify to the quality of their work. Ask contractors for price estimates for the installation. Be sure to receive a written, itemized list of the price estimate before the contractor starts the installation. Try to schedule the installation of your central air system during the spring or fall. Since these periods are the off-seasons for HVAC contractors, you may be able to find a lower price.

Summary:
Buy a central air conditioner to cool your entire home. Schedule a pre-installation evaluation. Find a licensed contractor to install your central air system.