​My mother wants to start her own business

I’m seeking advice on behalf of my mother. After years in a tiring desk job with long hours and low pay, she’s decided to start her own business. Me and my uncle will also help her in this. However, we have no prior experience in this field. Here are some questions we have:

How do you start a business from scratch? What are the essential things we should take care of when starting out as we are newbies? When is the right time for her to leave her job and focus fully on the business as she’s the only earning member of our family rn (me, my younger brother and my mom)? Please suggest some small business ideas which she can carry during her job and can make it large scale in future. Also advise us on how to grow it into large scale in future.

We’d deeply appreciate any tips, advice, or personal experiences you could share. Thank you all in advance for your support!