I’m making game where the player will be exploring a small town. It might change but right now I’m planning on have each building be a level. At what point should I consider level streaming sections of the building? Should I even consider it? If I do how could I handle if the stream splits two or more rooms. Thanks for any help 
When you building takes too much memory or building loads for way too long. Remember that loading level takes time and player will need to wait in that section of the building until new section loads, so having too much of them might be annoying.
Level streaming is for performance. It’s basic use is to break up a large map that would be difficult to render all at once.
You’ll want to start thinking about level streaming if you have a big map that you want to improve performance on, and make it seamless (no loading screens everywhere).
You’d split the map into sections, and its pretty tricky. You’d have to segment them in a way so that you only offload segments that the player can’t see, through windows, 360 degree turns, ect.
Check out this video about level streaming implemented by Firewatch. It’ll make everything much easier to understand, how difficult it is, and when you’d use it.
https://youtu.be/hTqmk1Zs_1I
I’ll definitely watch it thanks. A couple problems I’m already have is how to load a wall and or doors if my level streaming volume intersects with said wall or door. Secondly, rn I can save anywhere in the game but if I save in a streamed level and then load from anywhere but the persistent level, the stream level doesn’t load. I’m positive it’s because my stream volumes are attached to the persistent level. I’m the only person working on my game so I think a simpler solution to the second point would to have “save rooms” that are always loaded and only be able to save there.
You can have objects intersect the streaming volumes, as long as the player doesn’t see the loaded/offloaded objects as they’re streamed.
Save rooms are definitely nice, not just for level streaming but also organizing the rest of your game.