If the business is collateral, you have a couple of options. All of the legal options are likely to lead to a messing legal battle, as they all typically are.
The first step, if you haven't already done it, is to record the lien you have on the business and assets, depending on how the collateral is described. If you have a lien against the real property, that's a separate system as well.
The Second Step, if negotiations fail, is to sue for payment of the debt.
--We'll look at the misrepresentation claim your opponent may have right now. In order to satisfy a claim for misrepresentation, he must show you made a false statement of fact, directed towards him, that induced him to enter into the contract, and he suffered a loss because of it. In this case, it seems that he will have a hard time satisfying all four of those elements, so from what I know in these facts, you're fairly safe on that front.
At trial, you'll have to prove the debt (show the contract), and show nonpayment of the debt. If you win the trial, you'll get a judgment. You'll file that judgement with the clerk of court. You will then seek the assistance of the sheriff to repossess enough assets from the company to satisfy the debt, or you will be able to retake possession of the business to satisfy the debt. If you retake the business, you may owe your opponent money if the business is valued at a higher value than the contract was for.
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