All the doors inside the house are locked. I found 2 keys for the outside doors and 2 tokens, after that I can't find anything anywhere and I've searched thoroughly.
The keys will spawn depending on what note you picked up, for example one explains something about the closet by the stairs, the key will be on the stairs.
Keys are real life sized so they are small.
I've noticed people have had a hard time finding them which I will probably update the game to make them pop more.