Greetings. I’m new. I’ve had an Ender 5S1 for a month and I’m diving into Printing because I’m crazy like that 
Got an X1C coming. My main question is about licensing and selling these prints. I’m mainly interested in making things for friends and teaching my kids about engineering and design, but I’m going to end up with extra prints with all the practicing etc. Am I a bad person if I sell a few of them for cheap on Etsy? I’m not looking to make money I just want to give my kids the experience and not waste any 99% good prints.
You need to check the license of the models you download.
Everything you design yourself, you can basically sell unless it is a 1:1 copy of something protected by someone else.
If you download models, you have to check the license information provided. Most common are the “creative common” licenses, and there are quite a few variations.
If they do contain the “non commercial” part, often displayed by a crossed out dollar sign, it means you are not allowed to sell the printed parts. You could always ask the creator of these files you give you an exempt from that, but I wouldn’t hang my hopes high there.
Nearly every print you can download contains the “Attribution” part though, that means even if you are allowed to sell it as it is not marked as “non commercial”, you will have to attribute the author for his work. How you do that is not really defined, but adding a little card with the authors name and link to the file stating it was his work should be sufficient.
For non creative commons licenses, you will actually have to read the license information and see what is allowed and what not. I would even suggest doing that for CC licenses too if you are not sure what is required.
Additionally you have to check the software you use. Most “free” CAD systems (not all) are not intended for commercial use, as far as I know.
Thanks for the info guys, you confirm what I already know but don’t want to admit. I just want to be able to sell one or two for fun but really it needs to only be what I design. And thanks for the CAD info, I never thought the CAD system would have something built into the license for commercial production. Where can I find that information?
Check the license agreement or terms of use.
What software do you use?