I know I have this story somewhere. After the battle, Tony invites everyone to live at his place but only Clint and Bruce take him up on the offer. So they become friends. Then the others move in and I remember a scene where Natasha and Steve are outside and she says something like, "I guess we missed a lot by not moving in sooner"... or something like that. Vague I know but. Oh and I am 99.999 % sure it is on AO3.
Please, Please help because its driving me bonkers with a side order of nuts.