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I am sorry to hear about this situation.
1) A contract does not have to be notarized to be binding. So as long as he signed it, it is binding.
2) She can file a lawsuit against him as long as he is in default of the contract. This means behind on payment. (I am presuming that the contract does not dictate how much he has to be behind, so common law controls). As such, she can file suit against him as long as he is behind.
3) If he can, he should pay everything off at once (via certified mail). If not, he wants to pay whatever he feels is required to catch up to where he should be now.
4) If he and she disagree on how much has been paid and how much more he owes to catch up, then the Court will have to decide this, and the onus would be on her to file suit. Meaning, she has to do it. He should have been keeping clear track. She does not have to communicate and help him calculate how much he still owes (although her not doing so is childish).
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