I've recently had a bit of experience in this and (unsurprisingly) come up against some... I guess you'd call it prejudice (that might be too stronger word)? The stereotypical apprehension or discomfort some people have with shooters anyway, whatever you want to call it.
A while ago I found out a work-mate of mine had a hobby-farm/property here in Vic where they have sheep, cows etc. and the usual problems of foxes and rabbits. A few hundred acres.
This workmate and I have known each other for years, she knew I was into shooting and has no problem with it. She knows I go camping, hunting etc. I asked her if we could camp on the property and we would clean up a few of the foxes/rabbits for her. It's really her husbands hobby so she said she'd ask him which is fair enough.
Anyway, the answer came back that we could camp, but not shoot on the property. He has "a thing about guns" apparently. But here is the punchline...
They routinely have 4 blokes out on the property to do exactly what I was offering. *Unpaid*, but representing themselves as "professional".
I mentioned I'm licensed (obviously), an SSAA member with the public liability coverage etc. etc. More important she know's personally that I'm responsible and not an idiot. That didn't cut it for the husband though.
I don't know the husband at all, but he obviously has the picture in his head of me as some "gun toting amateur" while perceiving these other blokes as "professional". Dunno where the husband found them, but like Huccl said they're obviously not in the "business" pest control because they're doing it for free.
I know that sort of says people are getting invites, but I would think the vast majority are getting knocked back for the same reasons I was.
(I know that sounds like case of sour grapes but it's really not
just stating the facts)
If you've got access to a property that's great, but I wouldn't be holding my breath for invites via GumTree. Get out and find your own spots in the forest IMO.