Unsolicited Youtube "how-to" videos are not permitted. You are welcome to post instructional videos in response to a question or comment. You are not welcome to spam Youtube videos to the subreddit under the guise of "adding content".
6
Personal Sales
Ebay, Craigslist, and other personal sales are not permitted. This is not a marketplace and there is no reason to sell your content here. If you wish to sell things, do so in the proper channels (like r/hardwareswap). As an exception, if a user asks where they can buy something, you are free to provide them with links to sales at any of the above sites.