Having anxiety about my ability to provide for a family. What can I do to make it easier in myself?

Hey everyone, I(25M) have been dealing with a lot of self doubt and anxiety over my ability to provide for my fiance(25F) and our future children. Long story short, we want my fiance to stay home with our children but I am doubting my ability to provide for a family in one income. We have roughly 250k in the bank mixed from both of our savings and inheritance from a family death. I currently earn 75k a year but am next up for a promotion that will bring me to 90-100k. I am looking into different ways to bring in extra income. Mainly us purchasing a two family to live in at first and then eventually be our first rental. Do you guys have any experience or advice when it comes to providing for a family.