What is your day job? If your day job involves any of those things just quote them a comparable hourly rate and don't feel bad.

I usually let people know up front how much the service they are requesting is going to cost. A lot of the time this scares them away.

You could always try to work out some sort of service exchange. Given the people you are helping offer services that you'd want / need.

or you could learn to just say no.