Sole proprietor: hiring intern or part-time, locally or globally?

I've recently started my sole proprietor as my side job, so my experience is very limited in the administration part.

Currently looking into the possibility of passing some of my work to an intern or part time worker, haven't decided if I'll get someone in Japan or from different country.

Now I think, to my limited knowledge, I could hire someone as outsource, get them to send invoices and pay them. This could work in both local or global manner. Right?

However let's say I want to hire someone, what are the pitfalls that I should be careful about?

Example questions:

If hiring local person in Japan, both as intern or part-time, do I have to enroll them in some kind of insurance? Pension? Withhold income tax?

In case of hiring outside the country, are there any legal obligations on notifying someone? Is it even allowed to hire someone as intern/part-time who is not Japanese or inside Japan? Or I can't count them as legal employees?