I run a SaaS product that integrates with ERPs. I pretend to my customers that I have a team (so much so that I have multiple email addresses to people that don't exist that actually just forward to me). One of our customers thinks they're paying for a team of 6, but it's actually just me.
My monthly billings last month was 73k USD. I am a tax resident of a tax haven although I do live 3-6 months at a time in a different country.
The only advice I'd give anyone looking to build a lifestyle business is to keep your ambitions and by extension- product feature set in check. I know several other people who operate like me, and the common thread is we have businesses that can easily take VC funds, hire, and expand. But for lifestyle priorities, we chose not to.
A lot of people I've met (particularly in Chiang Mai, Thailand) copy popular, common, and easy online businesses such as drop shipping, social media XYZ, or coding. Unless you live in a really low cost area, it's not a good life. The key is have a very specific niche that can be scaled upwards if you want, but you always have the option not to. Those the ideas and businesses that seems to provide the ideal balance in lifestyle.
EDIT: The product came about at my last job where I built it to make my own job easier. Essentially it did 95% of what job which at the time enabled me to be the "best performer" while not actually working that hard.