Thank you for contacting justanswer.
You indicate that you have no formal agreement therefore the form and governance documents of the business partnership (if it was filed with the state) would control or state law may help. Failing any formal filings we can still review the law of the state if you will indicate the state in which the business is operating.
Typically the purchaser in the buyout in a business would pay you the one percent of the current assessed value of the business to return your investment in the business. If you do not have a current value of the business reflected in your accounting and financial statements you can bring in a third party business appraiser (your local accountant may be able to help or refer you to an appraiser if needed) to determine the value unless you previously agreed on your buyout return of funds.
A concern going forward is that unless your business associate agrees to indemnify you (protect you from any activity or financial activities related to the business) you may remain exposed to liability and tax issues. The buyout alone will not absolve you or those potential liabilities. The IRS, for example, will look back to the owners of the business at the time of any tax liabilities.
As an example, Onecle provides samples of indemnification agreements you may view to consider your buyout arrangement, especially depending on any risk associated with possible exposure to you, your local bar association lawyer referral service can provide you with attorneys you may interview as to their experience and fees in similar matters so that you may determine whether local lawyer review and involvement to protect your ongoing interests is needed.
I hope this information is helpful and responsive to your question. If you would like further clarification, particularly as to any law in your state that I may be able to reference, please let me know.