She said the people I was staying with could be arrested for harboring a runaway.
Correct.

What would happen if the cops came would they make me go home and could they get in trouble for letting me stay there.
You could be dragged home and they could be arrested.
Also could my mom get in trouble for making me pay bills.
No.
I want to get emancipated but ive heard it cost alot and it takes over 6 months which I would be 18 already then.
Not to mention, if your Mom objects - and it sounds like she would - it's game over.
What should I do?
Save up, and move out on your 18th birthday.