On that note, expect to lose money initially while optimizing your website & waiting for enough CPA data to accrue. I give it at least a month and $5-10k spend before seriously considering killing the campaign (if starting from scratch).

Very different from taking something already successful but mismanaged - this can be a lot easier to ramp off if they're making big mistakes (like not actually mobile optimized, not CPA bidding, not actually actively optimizing the website's funnel/landing page).