There used to be a recurring sketch/character on one of Paul Whitehouse/Harry Enfield's shows, about an estate agent who knew nothing but could only state the obvious (eg "this is the kitchen") and answered every question with "I don't know".
I didn't use to find it very funny, like most of their sketches it's a one-joke concept and it very quickly gets boring. (Tangent: Funny characters are one thing, but you have to do something with them, it seems to me. Whatever happened to jokes and wit?)
Anyway I now realise it wasn't intended as a joke or even a parody. It's a vicious expose of the real-life case.
When an estate agent takes someone to see a house, and that house is literally round the corner from the estate agent's office (one minute's walk), then you might expect the estate agent to know that the street that the house is on is a one-way street (has been for 10 years) and you might expect her not to bring the prospective buyers through a no-entry sign and drive their cars the wrong way up that one-way street.
You would apparently be wrong.
The first rule of selling is "know your product". Not "turn up with no knowledge or information and find out about it along with the people you are trying to sell to".