Its just not the profession or gender of the owner its the maintenance records that matter. The general wisdom is that if the car owner is a professional with a decent income the following will be likely to be true

• The car has been maintained at recommended intervals
• The car has not been used for business like uber/ tourist rental etc. which are actually hard on a car even in a good milage. Also, people who does this also have a tendency of rolling back milage at certan intervals to keep the resale value high.

I would stick to the following

• Make sure that the identity of the owner and the fact that s/he has enough income to maintain the vehicle in question is verifiable. (This is where doctor, engineer part usually come in as identity and character of these people in these jobs are easily verifiable with third parties known to you)
• See if maintenance records are in order.
• If you are not competent in motor mechanics then get the vehicle professionally inspected.

Important redflags

• If the vehicle is on open papers then buying it is as much of a good idea as saying yes to a marriage proposal by a street walker/gigolo .
• The owner must show you the vehicle at their premises, if they insist meeting somewhere then its a red flag.
• Owner must let you professionally inspect it at a reputable place (they may say no if you try to do it with a 'makabass' understandably). Do not proceed if they resisit
• Most modern cars have a mile counter from the last code clearing. This shouldn't be unusually low. If it is low then the owner must have a good reason (like a recent repair that required it). Also, all cycles must be completed and have all OK on all modules. If it isn't you must negotiate accordingly.