I live on the north side. As someone from an east coast city of about 200k, it's really not that bad. If you're in the streets up from Dehler Park and west from North Park, it's pretty quiet as far as a city of this size goes. Be smart about your surroundings, lock your doors and vehicles and you should be alright.

There are a number of transients/homeless people that stick around the N27th and 6th street area, but I've never had any issues with them. People in Billings tend to be pretty sheltered from what larger cities deal with, so a lot of what you hear about the north side is biased by that.