Escaping toxic job & going freelance (on spouse visa). How to best to prepare financially?

As the title reads, I'm about to resign from my really shitty, low-paying job here and go freelance for the first time in my life. I already have a casual writing gig lined up for all of 2026 and will also be using my time to skill up, finally sit the N2, job hunt, and make steps towards deciding if I really want to stay in Japan or go home with my Japanese spouse (who also isn't happy here right now).

For those here with knowledge and experience of freelancing in Japan, what do I need to know/be prepared for?
What changes will I experience in relation to finances, health insurance, pension payments, etc., as a freelancer?

It's a totally new direction for me, and I don't want to get screwed over by avoidable circumstances.
Thank you in advance to everyone who helps! <3

by Difficult_Cookie3887