Own private lessons for kids

I have heard of renting out a space and people doing classes for kids there like once a week. Has anyone done this?

I was wondering about tax issues, and if I have a Japanese friend doing it with me. I would like to do it all legal.

Thank you.

What visa or residence status do you hold?

I hold a 3 year Specialty in Humanities Visa, and work at a good place that can renew my visa. Thanks

If you are already working then the bigger issue, I think, is about your employer letting you have a second job
As far as tax is concerned, it should be simple process to add your additional income from lesson during your year end adjustment form, so that you pay income tax on that income