Excellent analysis. Negotiation is far cheaper than litigation. I'm convinced that the ownership interest of the other person is some place between 31.43% (thanks for doing that arithmetic, TM) and 50%. To get the 31.43% the OP will likely end up litigating away a portion of the value s/he is attempting to retain. At 50% s/he is likely leaving something on the table. Give the amount invested by the two parties, a 60/40 split that could avoid litigation may be in the best interest of both parties.