Some 20 evacuation orders are in place from the NSW Mid-North Coast to the Illawarra and western Sydney, with the SES warning the deluge will continue and more evacuations are likely.
Much of the Mid-North Coast region burnt out at the end of 2019 is now underwater.
Rob Costigan, from Pappinbarra near Wauchope, said losing his home after surviving fire and drought was a "kick in the guts".
"We battled through the fires in 2019 to save the place just to have it washed away," he told ABC TV on Monday.
"It is heart wrenching."
Mr Costigan was able to save his dogs but holds grave fears for his livestock.
"The neighbours are saying that things are hanging from trees," he said.
In nearby Port Macquarie, restaurateur Nathan Tomkins says the past few days have been a nightmare rollercoaster. After record flooding at the Hastings River over the weekend, Mr Tomkins' eatery was inundated with neck-high water. The venture he's spent 24 years building is in ruins.
"The water just went right through and just destroyed everything. There is nothing left," he told ABC TV.
"This is just like a nightmare, it really is."
It isn't over yet either, with much of the mid north coast bracing for more flooding on Monday.
"I'm feeling like I'm on a roller coaster. I woke up this morning and I just pinch myself to go, 'Okay, this is not real'. But it's real," he said.
Hundreds of homes have been damaged, including one washed down the Manning River at Taree, but Emergency Services Minister David Elliott says it is only a matter of time until lives are lost too.
The SES has conducted hundreds of flood rescues since last week and each one brings the state closer to an "inevitable fatality", he said.
It comes after police overnight rescued an elderly woman from deep floodwaters on the Central Coast after spotting her car by chance shortly before it was swept into a river.
The incident sparked a renewed warning for people not to drive on submerged roads.