Whether you're operating a shoe business or any other business, the amount you make as the owner of a small business should be roughly the same. It follows this general formula: Take the operating profit from the business, take out any amounts you have to pay to banks, other owners, or the government, and you keep the rest as your income. Not sure what the profits of your shoe business will be? Well that's simple: just figure out the revenue of your business (for example the number of shoes you sell times the price you charge for each shoe) minus all of the costs of designing, manufacturing, marketing, and retailing the shoe (don't forget to include any salaries you have to pay to employees). This is not an easy thing to do accurately, so you should look into creating a "business plan" for your business.
As you can tell, your income is going to depend entirely on the success of your business. When your business is thriving, you'll be well paid. When business is bad, you may not make any money at all (or even have to borrow money to keep the business going).
You're not alone. All entrepreneurs face this challenge. Without knowing how successful your business will be, it's hard to know how much money you're going to be able to make. Will you be able to pay for food? Rent? Family? Having been an entrepreneur in the myself, what I can tell you is that you're going to need to hustle extremely hard to get by at the beginning. It's not easy. But if you succeed, it will be extremely rewarding.
If I can give you one last piece of advice for this question, it would be that you should not create your first business alone. Find someone who has built a business like yours in the past, and ask them to become your coach as you build your business.