Related business and our model is similar and has been successful- selling a short, defined fixed deliverable (like your audit) that is primarily discovery on my end as a lead in.

Pros of this is the small financial commitment for them (compared to a full contract/project), allows me to get paid to deeply diagnose the problems, allows us both to make sure we’d like to work together, and provides them something of actual value even if they don’t decide to go forward.