i would suggest modelling everything in the same scene but render in separated layers, your house in a different layer your characters in a different one etc etc then composite everything in a software like Nuke or after effects or apple shake.
but if you're wanting to model everything in different scenes tho, you can then open your main scene and import everything as references, File - Reference Editor....then in that window File - Create Reference.
this won't change the file size, your main file will still be heavy, but you will just have more control over everything.
be aware though, this could be either a bad or a good thing, for example if your main scene is the house one and you reference your characters in it, then you go back to your character file and change something to it like your change your characters head it will also be updated in your main scene.
another good thing, in the image above if i uncheck HeadRN head.mb anything in that scene will disappear like it was never there, which will also reduce the load of the file