How

In May 2017 my husband decided to sell his motorcycle. We posted and ad and this couple came and looked at the bike. They came back next day and said they wanted to buy it. At time we did not know that they did not have the money but they asked could they make payments to us monthly. My husband said ok and we agreed on the amount they would pay monthly. We did not make a contract up did it as verbal. In June of 2017 my husband had a stroke then he had to have 2 brain surgeries. this couple got very spuratic in the way they were paying. I would call and text them but they always had an excuse. It is now January 2018 and bike is still not paid for. Selling price was 8500.00 and they still owe almost 4000.00. They never come and bring checks when they say and I have explained my situation to them as I have many medical bills and I need this bike paid off. We still have the bike here and still have to pay the monthly payment and insurance on it. I just need to know where I stand legally as