[someone]'s own master

Translations
[кто-то] сам себе хозяин
After starting his own business, he became his own master.
После открытия собственного бизнеса, он стал сам себе хозяином.
Definitions
A phrase used to describe a person who is independent, self-reliant, and not under the control or authority of others; someone who makes their own decisions and governs their own actions.