Disclaimer: I am not a proven entrepreneur—in many ways I am in the same situation that you are in and these are the opinions that I have formed trying to find an answer. And I look forward to learning from the responses you get from this community.
I think the software company should own the code, not the consulting firm. Unless you combine the two companies and you get 1/3 ownership in the consulting business/revenue as well.
My partners and I have thought long and hard about the difference between an owner and an employee. And what we should expect from each.
Right now you are performing both roles:
•Owner: passionate, innovative, entrepreneur, visionary, self-motivated, learner, leader , loves your product
•Employee: executes on the vision of the owners, task-oriented, may or may not possess the attributes of an owner
The reason you should get 1/3 of the company is because you are owner-material, not because you are a great employee. In the meantime while you are performing both roles, you should get paid a salary for the task you perform (based on time contributed) as soon as it’s possible—this keeps you from losing motivation to perform tasks while your company is too young to add employees. If you want to keep performing the tasks then great your passion as an owner will show in each task you perform. Eventually you may have to lead a team of developers to execute the tasks that you are doing early on.
So, if the company is making money/ get investor money and you are contributing full-time hours as an employee then you should get paid more than the others who are contributing less toward tasks. You could even be generating a back-log of hours toward execution of tasks to be compensated for later when possible. But all of you should be full-time owners or your business will be in trouble. That means that in everything you do/learn in life you ask yourself how it could be applied to grow your business.
If all of the tasks on the road-map are being generated by your partners then you are not stepping up as an owner—your ideas are just as valuable as theirs. Lead the technology arm of your business and contribute to the other areas that your co-owners are leading. Learn, learn, learn and contribute.
There are reasons that some of the most talented people in the world are performing tasks for other companies—they aren’t owners they are employees.
If your software company drives leads to the consulting firm then have the consulting firm then pay the software company if the lead becomes a customer. If the consulting firm drives leads to the software company then pay the software company if the lead becomes a customer.
Both businesses should be grown separately with a unique strategy for getting customers. There can definitely be a symbiotic relationship, but it’s survival of the fittest. Don’t let the needs of one company be detrimental to the growth of the other.
Remember the disclaimer above and good luck!