The simple answer: no. We do not recommend shopping for a used air conditioning system and calling a contractor to install it. (Or worse, trying to install it yourself!)
We know that purchasing used is often a great way to save money. Used books, furniture, cars, and laptops can all make good, cost-effective investments. But this doesn’t work for all purchases, and in the case of an HVAC system, it’s a major mistake. No reputable HVAC contractor will install a previously owned central air conditioner. The only case where you’ll hear about people buying used HVAC equipment is with window ACs—and even then, it’s not something we recommend.
(We don’t recommend window units, period. If your home doesn’t have ductwork, we advise looking into installing a ductless mini split system.)