I just bought an ’81 Honda CM400E as my first bike. It’s in great shape for being 27 years old and only has 18k on it. Runs awesome and has plenty of power for a first bike. As long as it was maintained well I don’t see a problem with buying something old. I also wouldn’t worry about it being air cooled. Tons of bikes are air cooled and I look at it as one less thing to go wrong in the long run.
If you guys really want to learn to work on bikes in addition to getting a bike to learn ride on I’d recommend picking up an old “basket case” that is saveable but needs a lot of work. If you completely restore/rebuild an old bike you’ll know it inside and out and learn a ton about working on bikes in the process. This way working on the bike won’t interfere with your riding.