Checking out public records of your friends, dates, landlords, or coworkers is entirely legal in itself. However, it would be best if you didn’t use it to perform background checks for the purposes of hiring or when deciding whether a person is eligible for loans, education, housing, and similar. It is also illegal to deny anyone these opportunities based on the TruthFinder report results.
TruthFinder’s privacy policy clearly outlines what the service is and isn’t suitable for, so make sure you read it beforehand.