What’s a fair price to rent out a room to family.

My sister asked if me and my husband can rent her and her boyfriend a room at our house. They have never lived together she lives with my parents and he lives with his grandma who is kicking him out. She is not kicking him out because he is a bad kid but his whole family is trash and he is a foster child and she just stopped getting money for him so she is kicking him to the curb. They are 19 years old.

I absolutely love my sister and would let her stay for free. But we are struggling ourselves and this could be good for all of us. My sister doesn’t have a job but her boyfriend just got a job working for Amazon I have no idea how much he makes. I’m really excited to have my sister living with us since we are really close.

The room they will be renting is a decent size bedroom and they will have their own bathroom. We also are gonna clear out the fridge/ freezer in the garage so they have their own. What in your opinion is a fair price for rent? Also we live in California