Nanny Shares are popular where I live in California however they seems to work differently than you describe. In example

Family A uses the nanny M/W/F and Family B uses the nanny T/TH

OR

Family A uses the nanny M-F 8AM - 2:00pm and Family B uses the nanny M-F from 3pm - 6:00pm

Both situations the children are in their own homes (not the nanny's home) and the two families children are not watched together. That this seems to reduce the "full time" cost of a nanny you really like,love, etc. by helping her have full time pay you will likely keep her longer but the hourly cost does not seem to be any less.

The providers above highlighted some very real issues and if you are around still checking this thread I wanted to add some potential solutions....

1) Since your nanny lives with you in the same home how about licensing yourself and her as a home day care? If she is licensed then she can care for more children in your home and your childcare cost would likely significantly reduce.

2) Have you considered opening a home daycare? Not sure it would be your cup of tea but if you are licensed (like I mentioned above) you could be her back up / sub OR you could run it and have her as an employee.

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