Up until about a year ago we were living next door to a family in suburban western Sydney, typical setting, quarter acre blocks etc... They started keeping chickens. At first it was just a few and it was OK. We had always got along really well, his kids would always be over playing with my kids in the front yard - footy, soccer, cricket... good stuff, just like the old days when I was growing up...
But then he started getting more and more in to not just keeping chickens for the eggs, but breeding them (to sell, some of them were fancy exotic breeds of chicken) and started keeping dozens... and I mean dozens. He used to keep the incubator in his bedroom FFS! At any given time he's have chicks popping out of their shells and chirping away in his f**king bedroom!!! This if course led to an increase in the mouse popluation around the immediate vicinity of his home - their house and garage was for all intents and purposes infested. We started seeing them in our house, I'd leave talon (rat/mouse poison) under the kicthen sink where I was sure they were getting in and it would be gnarled away in record time... I once found a rat in my backyard. By this time I was fuming so I killed the rat with a shovel and popped it in a plastic bag and brought it over to show him... He was apologetic but then started making excuses about how the rats were coming from the (underground) sewer line that ran all the way along the back fences of his and ours properties... it was lame, I just said, mate, every house has a sewer line around here but they're not getting rats and I'd never seen any until the chickens came along...
The worst part, if the mice and rats weren't bad enough, was the smell. With the amount of chickens he was keeping, coupled with the fact that he wasn't real vigilant in cleaning up after them, in the warmer months you'd walk out the back door and the stench of chicken shit was foul/fowl (take your pick!).... Plenty of the other neighbours obviously had lost patience too as a number of complaints were made to the council. But they were toothless... Inspection after inspection, but nothing was done about it... Sometimes in really hot weather in December/January, a few of the chickens would die from the heat and he'd throw the carcasses in to an open plastic drum/bin thingy on the side of his house. So the smell from that was horrendous until he disposed of them properly, and of course that was attracting more vermin.
In the end I confronted him and just said he needed to get rid of them or cull back to 3 or 4 only (which I think you're allowed to do)... He ended up giving them to a bloke he'd met as part of selling them online who lived on a few acres over Richmond or Windsor or something like that.
I could go on forever and while I know you're not planning on keeping the numbers this guy was, I would do the courteous thing and run it past your neighbours. To be honest, even keeping just 3 or 4 is going to attract mice and/or rats. You have to vigilant with cleaning up after them if you want to stay on your neighbours good side (in my experience).
Bottom line is, I think people who want to keep chickens should consider moving to semi-rural areas or acreages. In built up suburban areas, I just don't think it works, the downsides outweigh the upsides IMO
