1. Price-- low. Under $200...sometimes way under.
2. Ammo-- cheap and plentiful, especially Russian and Chinese manufacture. 7.62x39, same as used in the AK. There is at least one US-made rifle chambered for the stuff. Beware corrosive primers.
3. Range-- I have no trouble hitting a 1x1 foot target 150 meters out. Urban defensive combat should be at closer quarters just because of the buildings etc.
You can get a scope, but for your application, why?
I almost didn't mention the availability of hi-cap aftermarket mags. I personally find them over-large and inconvenient, and open the temptation to "spray and pray" which isn't a good idea in a populated area...even if you think most of the population is after you :)