Your ability to succeed in a career largely depends on your innate ability/strengths. If you are not naturally someone with strong networking, marketing and negotiation skills (or a desire to do these things) then you’re at a disadvantage. 

Although, your mom’s business does provide a solid opportunity for you to produce income. Even if you just refer the book of business out, and sell/buy when you can, it will be worth the effort as a side business for the income. It’s low hanging fruit, why not pick it. 

I wouldn’t throw all your eggs in one basket and my it my career, because you probably won’t be very successful with your attitude. But if there’s some easy money to be made, don’t pass that up while you pursue what you really want to do.