] Mrs. Bennet begins the story by exclaiming to her husband that Netherfield Park is 'let at last.' I was thinking of the reasons why it could been so difficult to let it in the first place:

I think because Mrs. Bennet is very worried about her daughter to get married, has put in her mind Netherfield and IMHO she was waiting impatiently for it to be let. May be it was for a few months but to her it was very long time . You can see how she feels about this matter when she says:

"If I can but see one of my daughters happily settled at Netherfield," said Mrs. Bennet to her husband, "and all the others equally well married, I shall have nothing to wish for."

It seems that was the only thing she was thinking of for a period of time. Also:

"At our time of life it is not so pleasant, I can tell you, to be making new acquaintance every day; but for your sakes, we would do any thing."
This leads us to another thing, to how considerate is she to devote her life to the best for her daughters (in her opinion of course).