I've researched about your question and found a few ideas /tips. Isuggest that you buy vehicle history reports prior to purchasing used ISF. This will help you to know the problems of your prospected ISF. Carfax or Autocheck are good but results aren't always sufficient and expensive. I prefer Vinaudit for cheap carfax history reports. They check title problems, prior damages, odometer, salvage, and other historical events. Never use free reports online as they aren't reliable. Dealers won't tell everything so better do some research yourself and bring a mechanic to test drive.