Most every class A or C will have both air and heat. The mentions about checking systems is important. When dealing with a rig in that age range, I'd spring 350+ or so dollars on an independent RV inspection, both mechanical and interior components. Then get the list of repairs needed and use that to negotiate price.
Take a small flashlight and look in every closet and cabinet for water damage or leaks. Check for softness of the floors, roof (yes you can walk on the roofs) as well as walls. Water damage, especially if undetected or ignored can be a cancer that can drain your wallet. Delamination is the devil too. Google delamination to see pictures of tell-tell signs of the bubbling that delam causes. It is an expensive repair, sometimes not worth the repair due to exceeding the value of the rig in question.
I like records. A well maintained rig should have an advantage over one not servied. Be aware of very low milage rigs and those with very low hours on the genset as both the rig and genset need to be exercised their life to help mitigate breakdowns.
Use your nose and your eyes, a lot. They will tell you volumes. Dealers will upcharge and you will probably find your best deal with a private sale. Google is your friend. Find an older couple looking to leave the RV lifestyle. In those deals you may get a rig fully loaded with all the camping gear and accessories you ever need. We did that with our first Class A. It was a great deal, and we even got a tow vehicle tossed into the deal.
Good luck and ask plenty of questions.