To be honest I think you might struggle to find a roadworthy bike for $1000!
I'd check craigslist & ebay if I was searching as everything in Autotrader will be $1500-$2000 and up.
You might have to 'take what you can get' for that sort of budget, basically I'd take anything that looks like it's been well-looked after.
I think you are in the realms of late 80s bikes, and of course something from the south of the country can be in perfect condition after 20 years due to no rain to rust it.
Maybe check out a Yamaha Radian 600 - a nice bike, and looks pretty sharp too IMHO. It's kind of in between a cruiser and a naked and the styling has aged very well (again, JMHO)
Ebay is your friend
Edit: At age 21 all you will be able to afford is liability insurance, but the type of bike will have a massive impact.
As an example, last year I paid $200 a year full coverage as a new rider aged 30 on a DR650 worth $5k.
Then I got a sportbike (ZX7R) and my premium shot up to $1500 a year for full coverage.
Liability only insurance on either bike was within $40 of each other - $90 a year for me on the DR650, and $130 a year on the ZX7R.
I think liability only on an R1 was $150 for me!
