if someone needed me to be in my own apt onthe weekends, I'd either expect them to pay for it or I'd expect to be there every night.

It is possible. I interviewed for a job and they needed the room on the weekends so would be expected to have an apartment for the weekends

Most parents don't know how to place effective advertisements for nannies.

Message them and ask

But why does it say: M-F live-in instead of: Live-in nanny, M-F 50hrs 7-5pm. Weekends off.

Its probably just your run of the mill live in job. You work a normal schedule M-F, evenings off, weekends off, and your room and board are part of your compensation. People may feel the need to specify that you'd get weekends off because of the increasing popularity of the 24/7 live-in nanny. *Some* people expect 24/7 availability simply by virtue of hiring a live-in nanny, the same way lots of parents assume sick day/snow day coverage or flexible end times when hiring a nanny without actually specifying this need in the agreement. Specifying M-F and weekends off lets potential candidates know that you aren't one of these boneheads.

I am seeing so many job listings (mostly in New York area) that say Live-in M-F. Weekends off.
Does this mean only live-in M-F, and weekends live-out? They do not say that they are 24hr jobs. And they don't pay like 24hr jobs- they are around $600-800 a week. They never specify hrs needed. Do you think that these are cheap people who are needing a 24hr, but are not paying for it. Or that you have a daily start and end time, and you can leave the house in the evenings if you want to? If so, what is the benifit in this situation to both nanny and employer?