Mishandled,
My local free paper has a regular group of Advertisements offering the sort of thing you are talking about. SO there are plenty of others doing it. You will compete against a serious number of youthful computer whizz-kids who are doing this kind of stuff for pocket money ( my son being one of them)
Few people would be comfortable letting you loose on their precious computer without some qualification in writing, so Microsoft Certification ( although of limited value) would be at least something to show you know what you are talking about.
I genuinely think you would struggle to earn a living. It might work as a second job.
Hope this helps
H