There are a few places holding hot ground around Ballarat, but all in all it's quite passive ground really. The hotter ground is miles further north.
You'll have no trouble finding gold with a new Minelab gold Vlf unit around $850 to $1200. You just have to nut them out though to get the best out of them. In fact once you have your 'style' down pat and know how to set one up correctly and detect correctly with it, and enjoy your days out, you should strike at least 7 out of 10 targets that you'd pick up with a PI unit.
Stay away from the multifrequency CTX and Etrac's, they have and still do find gold but are maddening to use on hot ground and cannot be set-up to bring out any brilliance for gold detecting (the American units like the 70khz Gold Bugs and 50khz and 14khz Whites simply do not cope in the same ground a Minelab Vlf does, they are only suited to quiet heaps or dead quiet ground, in which the are quite good at.
As for the second hand Minelab PI's, the SD2000, SD2100, SD2200, GP Xtreme, GP3000, GP3500, GP4000, GP4500 - each has a very slight improvement over the previous model, yet some previous models do have some advantages to later ones. And we all have our favourites amoungst them.
So whichever second hand PI is bought, it really does not matter in the end, as long as you set that unit up with a matching battery and amplifier and coil combinations that suit it, and use it to the best of your ability, you'll do just fine.
Bare in mind many spend hundreds of hours with a PI and haven't found gold yet, and some get onto it in their first run out. That's our lot in the detecting game.
It sounds like your keen on getting out into the sunshine and spending the day finding gold, and that you've looked at a few detectors on-line or in a shop, so what the hell, throw that goldpan in the shed and get stuck into it.
Detecting's a great hobby and it pays off. The best gold detector you can buy new is of coarse the GPX5000, $7500 by the time you're fully kitted up. $1000 and above gets you on to an earlier SD model, great machines! and it's not much money at all.
I must admit that I don't really understand why blokes don't want to upset their 'partner' by buying a detector. The girls spend more on make up and grooming products each year than we do on detectors.
(Put her in her place. You do whatever you want to do, toughen up)
PS. Having said all that, I'll add that buying the best new gold detecting unit on the market is the best way to go!
And that's coming from a bloke who'd still rather grab his old dual ace and big coil and head into the bush.