Investors in the Australian property market have enjoyed historically low interest rates ever since the GFC in 2008. The combination of a general global slowdown and the end of the mining boom corralled money into the property market and it quite literally exploded.
In some cases smelly drains are caused by the loss of the seal created by the plumbing trap. Basically this is where the water level in the trap drops below the u-bend in the pipe, allowing for the free passage of gasses back and forth.