I completely feel you. I was in the same situation but I respected myself and didn`t do it for free. It`s your time and time is money. Now if you want to do it for free to gain a few clients then start charging it`s a different story ! Play smart!
Personally I don’t charge my customers for a 5/10 minutes job.
I usually do little fixes for free to clients websites – but I also charge about 800.00 for the 10 hour jobs, which I complete over a few days in my free time.
My clients appreciate that I am there for them when they need the work done, and I don’t nickel and dime them to death.
I quote on a per job basis, and they like that.