When I was SDO back in 2011, there used to be a very famous quote there:
"... Do not trust your overseer / sub-engr., even if he is your father...! "
Similarly, do not blindly trust anyone while buying a car, plot, bike, etc. even if he is your relative, etc. Only Buy after thorough investigation.
You are spending your hard earned money, so its your right to thoroughly check and investigate, in fact, you must thoroughly check and investigate a car, etc. before buying it, from anyone.
Chalein ya to banda muft mein, ya aadhi price mein dey raha ho, phir to bgaaeer check kiay khareed lainay ki samajh b aati hai, otherwise, if you are buying at market rate (or slightly less), then do not buy before thorough checking and investigation.