Most businesses that call an analyst already know something is wrong. They just cannot say precisely what, or what it is costing them. That is the work: making it precise enough to act on.
A written proposal: what is happening now, what each problem costs, the options with numbers against them, and a recommended sequence. Not a slide deck of observations. Something you can act on or hand to a board.
The first conversation is free and usually enough to tell whether there is a real problem worth paying to solve. A full review is typically a few weeks depending on how many parts of the business are in scope.
No. "Profit is thinner than it should be" is a perfectly good starting point. Working out what is actually behind that is the job.