Some good points mentioned already. We manage mostly regional accounts between 500-6000 euro per month.
If a new client comes to us with a budget lower than that we actually advice to setup their own ads. Yes their CPCs will suffer and yes it will be riddled with mistakes. But it will still be cheaper for them than the mediaspend + our fee.
If they plan to increase the mediaspend in the near future, we advice that they invest in expertise from the beginning.