Cool!
Okay -- had you said from the outset you were looking for illustrator-partners in a fledgling company, I wouldn't have said a thing. I would have seen you as being on the right path for a low-to-no fund start-up.
Now, I understand, as should anyone entering into such a deal, that partner doesn't necessarily mean an equal share in contriolling the direction of the company.
From this point, two things become paramount; the busness plan and the contracts.
From this point I'm merely offering a possible structure to proceed. . . . understand that is worth exactly what you've paid for it --
You should have a reasonable idea how long and how many projects you will have completed prior to becoming a for-pay company.
An equitable system of shares for production should be implemented. The number of shares and how they are allocated should be pre-determined.
Require a minimum input within set periods, but allow for some personal or professional leeway. Those who fail to meet the minimum requirement have still earned their shares in the company, but will not be partners when the company leaves it's investment period.
At the end of your investment period you will have a concrete idea who really helped build the company and help you in making resource allocation decisions in the future.
Simply put, at the end of your investment period, you will know who walks and who just talks.
The partner shares can be broken down into straight percentages at this point -- each getting a share of the company profits over and above whatever rate the company is now paying for work/salary and what was agreed to be re-invested.
Contributors who failed to meet the minimum requirement would be given payment for their contributions at the first established rates as well as receive a one-time first year percentage of the annual profits. This would be the totallity of their compensation.
For artists and authors of complete works (especially those who do not become partners), a rights reversion x years after initial publication would be
a good move.
Hope this helps,
Richard