Seriously, I wouldn't waste a lot of money on courses. However there are TWO that I can recommend if you feel more comfortable with something that shows you the basics of selling online, especially on eBay and Amazon. I am NOT affiliated with either of these, so I do not benefit if you sign up. One is free.
The first one is:
StartupBros - You don't need a job...
They have a free webinar that gives you a good idea of the basics of how to import goods from China PROFITABLY and without resorting to selling counterfeits. Now, of course, they want to sell you their services - but the good news is that you can get enough information from the webinar to do it yourself - without having to buy anything. It is fairly basic, but for free, it could be very valuable for someone who has no idea where to begin. And they - as far as I can tell - do NOT hound you with high-pressure sales pitches to sign up. When I took the webinar, I received two follow up emails from them and that was it.
The second one I recommend is not free, but it does not cost very much compared to other courses and it has been around for a long time and has helped a lot of people to get started selling online:
Sell Online with eBay or Amazon - Tools and Tips, Instructions, Wholesale Products
Skip McGrath has a few things available at his website and they cover the basics of online selling, dropshipping and finding suppliers. I have only purchased one of his courses, for $79, a long time ago, but it gives you a good basic understanding of online selling. Many people swear by this guy and his stuff is pretty much hype free and realistic. It's at least worth looking at his website and if money is not an issue for you, then it may be $79 well spent.
I would stay away from any expensive courses, because they really have NOT figured out the secrets of the universe - they have simply figured out how to get people to pay thousands of dollars for what is very likely to be basic information. There is NO source of $100 iPhones, you DO need at least SOME money to get started selling online - even if you dropship (which I don't recommend) and nobody has figured out how to suspend the normal rules of business and make a zillion dollars from nothing, in 30 days or less, with no money to start with and no work involved. That is a fantasy.
I almost forgot... If you are looking to sell from your own website, rather than through eBay or Amazon, then Aspkin's
SixFigureBoss: Create Your Own Online Business! might be what you are looking for. I have been selling online for years and had been driving my eBay and Amazon customers to my website for a long time, but I had never quite mastered Google Adwords or had much success with it. When Aspkin put out his guide, I bought one and it was VERY valuable to me, because it immediately showed me what I was doing wrong with Adwords. I tried it again, using his advice and now my Adword buys are PROFITABLE! So, I wanted to mention that. But if you are just starting out, I recommend selling on eBay and Amazon first, because as much as we all bitch about them, they DO have the eyeballs! Setting up a website is something that I recommend to everyone, but it is NOT instant money and it can take months before it becomes profitable. Mine was not profitable for at least six months and probably longer than that. But the work pays off in the end and it gives me something that eBay and Amazon can NEVER shut down.