Sales Agreements: Private Sale Repo

My question involves a consumer law issue in the State of: Georgia
I mad a deal with a "friend" to buy a car from him. He has allowed late payments before its never been a problem. This time he decided to repo the car. My question is this. Ive see where if the lender has allowed late payments in the months leading to the repo, the lender has to send notice that that will no longer accept late payments or that the loan is about to go into default.
Is this true of a private deal as well?

Sales Agreements: Private Sale Repo