first off, W O W !!

i completely see where you're coming from, BUT i would say do not stress too hard on your SS GF getting a job and helping because if he does not want her to live off him he would put a stop to it. she has gotten content in her position because HE is not making her move from it, so to her and possibly him , you and DH and his mother's opinion really doesn't matter, first of all , if he makes roughly 2500 a mth , wth is he doing with his money, that's his mothers problem she created a problem and now that is hurting her she is calling for help. NO ! NO WAY ! he needs to get off his grown behind and pay his own bills, i would not come out of my pocket and out of my household UNLESS it was emergency, if he wanted to live with and off of mommy he should have stayed home. im 22 years old and pay my own rent and dont ask my mother or in laws for a dime EVER !! Why ?! because when i thought i was ready to move out they laid it on the line , my checks go to my bills and whats left i leave for myself.

so i would say if his own mother does not put a stop to it or DH doesnt do anything, wash your hands with it. dont stress , just when/ if it comes to the point where he has to move back in , they will see what you were saying.