Hah - spend enough time on here and you'll get overwhelmed with options!
Having recently been through this moving from two oztents to a CT, you'll appreciate a good nights sleep on a nice mattress
- good quality pre-loved is the way to go for your first one IMO. You will find plenty around in that budget $5-10K. The good thing about that is if you don't like it, the cost won't be too bad, and you can re-sell at a similar price. You could even get a brand new Customline for around $10k. I bought a second hand one that I didn't have to do anything.
Think about what style of camping you want and work out from there. We actually use a rear fold softfloor and an Oztent, rather than side fold with a big main tent with lots of extra rooms. It suits our style of camping better (minimalist) and gives us more flexibility, but we've compromised on tent space - they're definitely smaller than the side folds. We spend most time outside so big main rooms don't do it for us - though still more than just in a tent. For other campers big rooms are important. So it depends on what you want. I actually wanted a rear fold hard floor but they are out of our budget at the moment
Rearfold footprints also resemble a caravan so fit in more places easily than the huge 14" Taj Mahal campertrailers I see around Xmas and Easter
You'll see plenty of newish campertrailers around, mostly imports advertised as "hardly used', "only used twice etc". Usually because they are a real pain to set up. Before I get flamed, I'm not bagging all imports but that's what I found.
Something we also considered was a good offroad trailer with an Oztrail tent bolted on top- would cost you about $5-6k, and a nice blank canvas to start with (this is just by way of an eg:
http://www.sydney-camper-trailers.com.au/product/off-road-venturer/)
If you are planning on getting off road then I would suggest that you make sure what you buy has an off road hitch of some sort. Saves you having to replace it later.