Without knowing your location or what ypu are doing for marketing, how can anyone give you the answer you want. Most
likely the answer is none unless you already have people asking you to shoot their pirtraits in which case you know the
answer for the first month. The second month will jave something to do with how many of those people then refer you to
other people, etc.
But from a cold start, a safe bet for at least the first six months is zero.