Not going to lie Facebook has brought me over 50 quotes in a couple of years.
however I pay now and again to sponsor my page wich means anyone who likes it, their friends see it, and it gets passed around that way.
What I will say is, when you receive a message off the potential customer always say "hello, are you wanting a one off clean or would you like to join our monthly cleaning service"
This usually sorts out the "full time mummy's wanting a once 10yearly clean"
Deffo worth doing if you know how to advertise on fbook