How do you forecast growth and traction rate on a pre-revenue startup that is still in private beta?
Your profile says '' ... I have founded and sold multiple businesses in the past ...''
So it means you should know how it goes.
Need to review (corresponding) industry annual reports and focus on it's figures.
Traction rate depends on your delivered services/product. If you deliver what your customer really needs, your traction will be very high and vice versa.
This is standard financial modeling. As ReMi said, you look at companies that do the kinds of things you do and how they exist today. You make educated guesses on how closely your circumstances will match the standards. And you make multiple models that show the most conservative and the most likely and the most fortunate outcomes. You base your decisions on the most conservative and hope for the most fortunate. If you cannot survive financially on the most conservative outcome (the expenses/income don't balance), then you need to revise your overall plan to address the areas of weakness.
I also agree with ReMi that asking this question on the third (or later) go'round puts the veracity of your profile in question.
I share same thought with Paul. But one area I would like to add if you're not a vet as your profile suggests is that, you can leverage goal setting. That is if you don't have previous data to rely on in making your forecast.
Set some goals for your self and seek to project how much you will likely burn in reaching such goal. Note that while you project your income and expense, it is a good thing to be as conservative as positive. I like to set higher estimates for expense and down my projected income.
Again, think of the best alternative rout routs to reaching your goals. What is the low hanging fruit among the many marketing strategies? Distribution channel. Which is cheaper when it comes to logistics etc.
Going this way might help you make a meaning projection that you need where you lack prior data to work with.
Remember it is a growth forecast. It is at best aan executive guess. When you start off, you might need to tweak your plans and forecast to suit the realities . Good