If the owner is available at the spot and is dealing directly with you only then assume the car is first owner or ghar ki gaari.
The specific phrases used by dealers pretending to be genuine owners like 'ye chachu ki gari hai wo bahir hotay' and the likes are all BS.
Even then its tricky as Ive seen people give their personal cars to part time rental especially during wedding seasons, etc.
For example a friend of mine owns a Corolla, is a first owner, uses his car for his personal use but has also given it as a part time rental to a construction company. He uses his other car when the Corolla is away.
So its always a gamble
I think these things should not really matter. If the car is in good nick with complete documents number of owners, dealer etc dont matter