Custom and sports bikes are worlds apart, I don't know the market in the US but surely you can get a cheaper jap custom, Yamaha did a XV model that was available (I believe in 250, 535, 750 & 1100 cc) various engine sizes, a nice comfortable cheaper alternative you could always progress to a Harley.
I would steer away from anything bigger than 600cc as a beginner, from experience (65k miles a yr by bike) new riders have an accident (it depends as to you luck whether its a minor or serious one) within 1-2 years usually non fault but due to not expecting car drivers to do the unexpected!! Gain the bike & road experience on a smaller used bike first at least you wont feel so bad when you drop it, every one does at one point!