Building minibikes?

Hi all, I want to get into building bikes/projects and if I can find a job back in my hometown I’ll have a small area to work on projects. I was thinking of getting mini bikes (like the kids sports bikes) and working on those for fun as I can learn how engines/centrifugal clutches work and transfer that to bigger projects when I have much more space. Is this a good idea? my brother has berated me for it because there’s “no money” but its not abt the money