It is unnecessary to include a detailed budget in the letter, but an overall cost estimate should be mentioned. This sentence should be followed by one describing the program, the agency, and another one or two concerning the need for and uniqueness of the project. The body of the letter should consist of three or four paragraphs giving some context, background, scope and methodology of the project, time frame, agency commitments, and special capabilities. A separate paragraph might be devoted to some of the major categories of the proposed budget including a rounded total direct cost estimate, administrative costs, if any, and the mention of any matching funds or cost sharing arrangements, either in dollars or in-kind contributions. I look forward to hearing from you soon.
Foundations usually respond within a matter of weeks.
That custom allows you to establish a pyramid of likely prospects and to approach them sequentially within a relatively short period of time.