You’re on the right tract here. 500 CC’s is a good range to start in. Check out some of these articles. As far bikes, if you are after a cruiser and want a harley in the future, do your research on the Vulcan or like bike.
And for SAG’s here is the ninja 500.
I ride a ninja 500 and love it. I also love the fact that you don’t really get into trouble on it until you about 7k RPM’s. That’s when I feel the bike really comes alive!