Through out this few years in business, I learn not to judge a person as good /bad at the beginning because normally, they need you and they want your trust. Then after some times, they become more like your friends and you take off your security guard & give credits up front on your sales. It's when the things went wrong.
Recently, I got a couple of invoice I couldn't get the money back because
1) customer closed the business and had no money to pay back
2) customer changed to another supplier, so he doesn't need me.