So , can you give an average amout of money that an Escrow earns in a month ?
No noone can. It all depends on how much deals you will get, how big your deals are, and all that depends on how trustworthy you are.
Right now you will probably get 0$ through escrowing other people's deals, due to the fact that you have no reputation here on this forum.
It will probably take a long time before you have that reputation to make a decent amount with escrowing..