Answer:
The Narrator didn't believe Herbert at first because Herbert appeared to be very poor, and he thought he was not going to make any money off him.
Explanation:
The Foster Portfolio is about an investment broker who was called by Herbert Foster to look at his portfolio and manage it.
He went to Herbert's house for that purpose but was initially disappointed with the general lack of affluence of the household and its occupants.
According to the narrator "my business is handling other people’s money, and I have a great respect for money" and that he is "a salesman of good advice for rich people", so he couldn't see how he could help a man who appeared to be neither rich nor to have any money to speak of.
That was why he didn't beleive Herbert was in ned of his services.
