How much should I charge??

Ladies my lil brother 19 moved in with my SO and I. He's still searching for a job he went to a job interview today. He said he will pay us rent when he gets his first check. I hate charging but we need help to especially if he stays here, eats our food, uses the electricity and water. I'm not complaining I love him here but it will help alot if he helps. Well he was talking about giving us 500$ a month but i was like no that's way too much. Especially since we pay 905$ a month, internet (he also uses) 75$ and utilities around 50,60,80s. Well my SO and I dont know what to charge. Right now he's laying on our couch in the living room since we only have a 1 bedroom. What do you think we should charge him when he gets a job?? Again I don't care he stays here but we also need help with bills it'll be helpful for us. We are also helping him out since he dont have anywhere to stay his gf comes Friday, Saturday and Sunday to also spend the night which I don't mind just threw it in there.