So a man should not only avoid yichud with a babysitter but also avoid developing any meaningful relationship at all.
Yichud is permitted if there is a shomer present such as a daughter from about the age of five or a son from about the age of six. At this age they will understand when something inappropriate is going on.
One also must be careful about yichud with a cleaning lady, even if he finds her only slightly less attractive than a door knob.
If there is a cleaning girl over, thank Hashem you can afford one and open the front door so that anyone can walk in at any time. Alternatively, give the neighbor a key and ask him to walk in randomly [unless libo gas boh, which birtzos Hashem, we will explain].