My first mistake in buying used ski's for my son was finding a hardly used pair of skis with perfect tops and slightly used bases and it wasn't until after buying them that I found out that the only season they were used in was over 10 years ago and the shop won't work on the "Like New" bindings. Ugh.
The nearest Ski shop to me is just under 2 hours away but I have learned since buying those skis that there are season rentals from ski shops not on the mountain. I don't know why but I never realized this until I started looking for a shop to mount the bindings. Better selection of seasonal rental skis for a better price than the mountain... just about worth the drive.
Any other first time buyer mistakes the general skiing populous could share with us newbies?
Well, I haven't checked this website in a while, but it's time to help someone. I do not pretend to be an expert. Some other posts, above, make sense.
1) "You get what you pay for" is Very True when it comes to ski gear. If your son is still growing a lot, then renting makes sense, because the boots in particular will soon be outgrown.
2) Yes, friends with lots of skiing years & experience told me that bindings manufacturers put out lists of bindings that they no longer will service or support. If the OEMs - Original Equipment Manufacturers - don't support them, then local shops won't. They can't, they don't want the potential liability if the obsolete bindings malfunction, G-d forbid.
3) Yes, Boots -- if you're going to buy them, then please ask around about bootfitters in your area, and get them properly fit. I also got the "Instaprint" custom-molded inserts and they definitely helped.
a) My mistake: the first time I bought skis & bindings, poles and boots, I fit the boots myself. The staff were insufficiently attentive. A couple of years later, that store went out of business. Two seasons of those boots, and I noted, to a very knowledgeable new friend, that the boots already "felt like they were loosening up". He checked the fit, and immediately told me I needed different boots! Fortunately, he found friends - on a ski forum - that recommended an excellent shop in my area. WOW! I invested in new boots, with the custom-molded insoles, and it made a huge difference for the better!
4) Lessons - Absolutely, positively! I call them "an Investment in Safety" which let you enjoy skiing more.
I hope this helps. Good Luck, and Happy [Ski] Trails to You and Your Family, Dave