Poop, there are plenty of second hand good quality boards out there, but for a 90kg body weight, make sure you till have a bit of volume.
That means, over 9 feet, plus some width and thickness of at least three inches. Some boards, like Celarwater, but Stve Del Rosso and Diverse, buty Dave Verral include volumetric measurements, which help immensely with float, which is what you need if you're new to paddling a longboard.
Worth checking out Diverse in Tugun, they have some great high volume boards in stock second hand. As do Board Culture, and if you get in touch with Mac, he'll take you in and screw a price for you. Chrispy could intro you to SDR if you want something made, but above all, go for volume.
I manage to pick up a Diverse from a guy in Newcastle with a leash and Balin expandable travel bag for $450. 10'1" x 23.5 x 3.5 with 94 Litre volume, and it paddles like a canoe, easy wave catcher and would be a great nose rider, if I actually knew how to nose ride
Keep looking.