I've alway babysat in the neighborhoods I worked in. Never an issue. Just as long as it didn't affect my work hours or schedule. Usually I give my nanny family first choice to hours.
The only time it was hard was when MB was home on maternity leave and needed me part time. I helped out another mom part time during that period. It was hard for my toddler charge, who I have been with since infancy, to see me with other kids and not understand why I couldn't stay with him the whole time. However, mom was there with him and was so understanding.