Wow, tough situation, tough question to be asking. There isn't a book somewhere that has this kind of thing written down. Ownership normally starts with shares, like shares of stock, even in small businesses. There are no formulas.
You should probably be talking about this to an attorney.
Question added to topic Grow Your Business • September 18, 2008
How do you put a dollar value on 19 years of sweat equity?
I'm referring to a farm owned outright by my husband's mother.