Modeling advice

Hi , im looking at modeling a little scene and im looking for some advice , i want a short animation where my character moves from one room to another then heads outside and walks down a street . What my issue is im not sure about sizes , i want everything to be in proportion so that nothing looks ridiculously to large or small etc and when outside i dont want my character to look out of place. I Hope someone gets the jist of what im trying to explain and may be able to advice

1 blender unit = 1 meter. you should be able to model and assemble your scene with this scale and everything should look realistic.

You can change your unit system to metric in scene properties > Units > unit system, so all measurements would be in cm or meters.