I think the best course you can get is your own. Just start working on your bike. If you not sure of something you've got the biggest ever mine of knowledge - the internet. When I've started with bikes no one even heard about the internet

So at that time every biker could only relay on themselves or share and exchange the single-track wisdom with others. You guys better save that money and ask yourselves a question "How you learned to walk? On your own or someone explained it to you?

If you not going to start working on your own bikes there is no course that will make you a bike mechanic. Know how is already here on the internet so you better get yourself something new to your bike for that money and fit it yourself, or if you prefer go for a pint

And share the knowledge between each other.
I would even suggest organising some kind of weekend workshop where we could meet up share what we know. You buying some new part or would like to adjust something or gat an advice let’s say once a month in some place. Everyone takes tools they have got and we’re working on our bikes for a few hours asking questions each other and helping each other. To take it even further during the workshops we can record a video tutorials.