My answer to What should I know before becoming a partner at a small company?
Answer by Ken Larson:
Ask to see the business plan.
If there is no plan but you believe the business idea or operation has promise, develop a plan with the co-owner(s)
Then write and execute an operating agreement among the partners that identifies roles, % of ownership, who can sign for the business and similar important matters. Y0u may examine a sample agreement free of charge in the BOX at the left margin of the site linked below:
After the above has been completed make sure you are added to the articles of incorporation on file with the state and with the IRS.