We’re a family of 4 and we moved to SF from the North East about a year ago.
The babysitter would be asked to bring my 4 year old school (after I’ve gotten her ready) and then come back to help with the 3 month old. The babysitter would not be taking care of both children at the same time. Light housework is expected.
Schedule is relatively flexible. Alternately, the babysitter could pick up my older daughter from school instead of dropping her off and come in the afternoon instead.