Get what you like the look of! CB500s look a bit boring, rode a couple when I passed my bike test (in 2000) and they didn't inspire me at all. I bought a jap import 400 at the time – the Honda CB-1 (looks a bit like a Hornet but with the gear driven cam engine from the CBR400RR.
I was always concerned that a small capacity bike would look a bit small to ride (I'm 6' 1") but it was great to ride.
Paid £1,200 from a dealer but even then it was 10 years old. Sold it 4 years later for £1,000 and wish I still had it. Looking at any of the jap 400 imports they're going to be getting on for 20 years old now, so it might be a struggle to get anything that's not knackered…
I mistakenly thought that the best first bikes had no fairing to damage if you dropped it (I never did with the 400, but obviously watched my CBR600 keel over a week after buying it….) and to keep your max speed down a bit (that bit was true, but always unsure if there's any benefit to crashing at 110 instead of 140 – you'll be dead either way!).
Just get something you fancy and can afford, chances are you'll change it after a couple of years anyway – and there's always a demand for cheap bikes so you shouldn't lose too much on it. If you're really hung up on a bigger looking bike there are big trailies like the Honda Transalp etc that are cheap to insure, but they're a bit remote to ride. I've always preferred sporty bikes – had a go on a pal's 2009 Fireblade the other day and it's titchy!