RentPix is the ultimate app for car rental companies. Just give the app to your employees and they can take detailed photos of the vehicle at the start and end of the rental, and upload a zipped package containing these photos to Google Drive when they are done. The app stores date, time and location information in the picture EXIF data, and also stamps the date and time on the picture itself.
This quickly resolves disputes about damage, meets insurance carrier requirements, and leads to more trust between you and your customers.