Cash in hands is a must! And proof of insurance. A gal tried to pull a fast one on me when I sold a bike a while back. She was kind of short and almost crashed on my driveway....Twice. Each time I did catch her before the bike tiped over. After the second attempt I told her no more and she left. 2 days later she called and told me that she injured her ankle on my bike, needed some x ray and that she had no insurance..... I told her to f-off and that since my driveway is under video surveillance I had a proof she didn't fell..... Never heard of her again.