When Jane goes to Thornfield, she spends some time there before she actually means the man of the house. In chapter 11, Jane learns about the man of the house with these wry comments.
“Yes,” she said, it is a pretty place: but I fear it will be getting out of order, unless Mr. Rochester should take it into his head to come and reside here permanently; or, at least, visit it rather oftener: great houses and fine grounds require the presence of the proprietor.” (enotes etext pdf. 73)
Mrs. Fairfax’s humorous remarks describe Rochester as a man who does not spend a lot of time at home, and is rich but does not care much about keeping up appearances. She explains how he makes rare, sudden and unexpected visits. He is describes as having “a gentleman’s tastes and habits” (p. 76). He is also of “unimpeachable” character and is “rather peculiar” (p. 76).
[You] feel it when he speaks to you: you can not be always sure whether he is in jest or earnest, whether he is pleased, or the contrary; you don't thoroughly understand him, in short—at least, I don't. (p. 76)
Jane, and the reader, are therefore well prepared for Mr. Rochester to be odd, exacting, quirky and witty. In many ways, he is just that. However, by preparing Jane and the reader ahead of time, Bronte establishes a baseline for us to compare to, as we create our own ideas. In this way, we will be even more interested to see what he is really like, and examine the nuances of his complex behavior.
All page numbers are from the enotes etext pdf found on the first link.