My 16 year old brother wants to move in an apt with me and he will pay all the rent is it a good idea?

It sounds a great idea. Even if it doesn't work out long term. Move on a trial basis; keep your options open. If u get on well with your brother it will be a break for both of you and a rest for your parents and it is easier to run a home together as u can take turns with the chores. The only snag i can think of is the minding of your child when u both want to go out and when u can't take baby with u. Still, i guess u can ask good old mom!