Your budget is a big part of creating a marketing plan and should be decided upon at the start of the marketing plan development. After all, it would make sense to have your marketing consultant include billboard, print media, or television advertising in your marketing plan if you do not have enough budget dollars to ever implement the advertising recommendations or you want to stick to a specific budgetary amount.
By being upfront and completely honest about your budget with your marketing consultant, you will maximize your budget and save time and effort by avoiding research and time spent on pursuing marketing strategies you are never going to use.
A great place to start is to work with a professional marketing consultant to develop a strategic marketing plan for your business.