While not strictly required, maintaining detailed records of the sale would be ideal. If the amount paid was very low or abnormally low (e.g. sales for $1), PA reserves the right to investigate and tax the actual value of the car.

You'll want to work with someplace that specializes in vehicle titling. Some notaries will decline to handle titles.

Penndot has information, too: https://www.dmv.pa.gov/VEHICLE-SERVICES/Title-Registration/Pages/Buying-a-Vehicle.aspx