I picked up my Early 2015 11-inch i7/8GB air for $100 on eBay because the seller could not get the laptop to power on so they put it for sale as a "parts" laptop. I purchased it, connected the laptop to an AC source using a spare AC adapter I had and after a few hours performed an SMC reset and my laptop fired right up. I have since installed a 1TB NVMe M.2 storage drive with a Sintech adapter and have Mac OS 12 Monterey installed. It performes very well and I use this laptop today.
What I love about the Air is that the battery is so much easier to replace than the batteries on the Retina MBP. A few screws, unplug the battery from the logic board and swap. It is that easy... I also love just how fast and light this laptop is using the NVMe storage drive.
These laptops will run a little on the warm side. This is perfectly normal and not of concern. What you can do if you want is to take off the CPU heat sink and refresh the CPU thermal paste. It is very easy to do and whenever I source my laptops from eBay (see sig below) I always refresh the CPU thermal paste. Peace of mind that way.