Some states have a system you can run it through for a small fee. Arizona has one. Not sure about the others. I recently bought a camper and it had a lien on it. The sellers included a lien release that was originally signed and notarized by the bank and I had no problem getting a title certificate for it, but of course I was nervous.
In theory there's no such thing as a "secret lien," but in reality that can prove to not be the case. Short of buying from a dealer, I'm not sure you can ever be 100% sure.