I recently received an offer letter from an employer. During the interview, the manager said that they cannot give me an exact number before they calculate the budget (or something similar I cannot remember, although I did provide the expected salary at the very first interview and he definitely knew it), which did not leave me a fair chance to negotiate the salary during the interview.
The offer letter I received shows a salary that is much lower than I expected. I would like to know: is it appropriate/common to negotiate the salary after receiving the offer letter? Will this affect the offer or make them reconsider whether they should hire me?