Bullshit. I’m a freelancer. I know my monthly income. Why? I have a long term relationship with all of my customers. I never work project based.
If there is a new customer, I turn him asap in a long term one. How? Divide the project in smaller budget slices and invoice upfront monthly.
1/ you know monthly what budget you can work with and you have a fix revenue
2/ your customer knows his monthly fix cost and get used to it and understands quickly you become a part of his organisation and the need for a developer nowadays as fix part of your organisation.
Or am I a freelancer shifting to a studio … or agency?