How someone whose has variable income creating budget

Thanks for internet that helps us to work online and make money online. We can make money by making business presentation for other people. If they like, they may pay you dozen or thousand dollar. The company can pay less than hire some employer. For the self employed people, they may receive more or less revenue, depending on their project. When they got abundant project, they may receive more money.
Someday, Company will employ freelancer than employer to cut the company expenses.  In future, the company just pays the salary without pension fund, health insurance, and others.
As a freelancer or self employed, they may receive uncertainty revenue or variable income. Sometimes they receive dozen dollar or sometimes they receive nothing. To create budget for freelancer or self employed, they may calculate yearly income. Find the average of your income by dividing income by twelve.
Though you have no fixed income, you should allocate your some expenses. List also that you expenses monthly that you have expenses. Compute grocery food, water bill, electric bill, and cable bill, and others.  The spending side is relative fixed than the income. You must adjust the average of your income to the spending. Do not spend more than you can earn or you will borrow money to cover your high spending.
As a freelancer, we can estimate when we receive the income base on last year experience. For example, the auditor will receive abundant money in March because the jobs or project is abundant in March. There are so many companies that find audit service. Do not use the money for spending only. Some people may spend the money for useless gadget whereas use it wisely and you can put it at emergency fund that you can withdraw it whenever you need money.
In my opinion, emergency fund is very important for the people who have no fixed income. They can use it whenever they have no jobs or project. I think they are better to provide at least six month of your monthly spending. Increasing it double is also wise decision.