Generally, for a FT live-in. The rate is 2-4$ leas per hour. This can vary on the type of accommodations provided ( room only up to completely separate suite with kitchen and private entrance) and other perks (like full board, car, etc)
For part- time, 10-15 hours is usually done as a strict exchange for room-board. Anything between you can adjust on a sliding scale.
Note that live ins are still hourly workers and must be paid for every hour they work.