If
[I won't even get out of my bed for that kind of cash] < A * B <
[I feel embarrassed to ask this fee for my service]
Then
110% * A * B = [Your first offer].
If
[Clients words] = ["Know what, we have a deal at A * B"]
Then
[First offer to your next client] = A * B * 120%]
Etcetera.
You should consider the trade-off between how much you could earn with X units of time running your own campaigns versus spending that same time on someone else's. That catch-22 is that the best marketers apply the knowledge for themselves (ex: great hedge fund managers don't become retail stockbrokers). The economist in me says: Think opportunity cost.
If you do want to take on a client, consider the basic amount of time necessary for handholding and general status. When I paid someone else to manage my campaigns, I paid between 3-5% of ad spend. But that was on $300K monthly spend. That percentage on $1K a month is not worth anyone's time. Clients that have smaller budgets will incur a higher percentage.
The industry seems to charge based on a fixed percentage spend, which doesn't encourage performance-- after all, just spend more, so that your fee is larger. If your client is creative and if you believe in your skills, try to negotiate a kicker that is based on certain volume and CPA goals. Then you both have your interests aligned.
Hope that's helpful and let us know what happens.
dennisyu