Advice on breaking my lease-due to brothel upstairs??!?

Maybe you should notify the authorities. Anyone engaging in illegal activities is subject to arrest and prosecution. The other issue is whether running a "business" out of a residence is permissible according to local or municipal ordinances. Maybe the municipality will shut them down if they know about this and can prove it. The remaining question is whether there is sufficient proof of this misconduct other than your neighbor's statement. If you notify the landlord, you still may not be able to get out of your lease as soon as you like since your landlord is more likely to evict the miscreants.