Greetings,
Carfax is a good start before purchasing a vehicle, at a minimum to confirm that the title is not a salvage title. Be warned that Carfax only covers things that were reported. So if a vehicle was in an accident and repaired, but never reported to the insurance company, that accident wouldn't be listed on Carfax.
I made sure to get a Carfax report before buying my 2005 Safari.