Whatever you do, I strongly suggest you do not buy new. The depreciation curve on a new motorcycle is a cliff.
My advice for any first motorcycle purchase: Small, Cheap, and
Used.
The internet is full of stories of guys who spent upwards of $10k on that shiny Harley they'd been dreaming about since high school and they're heartbroken when they dump it in the parking lot on the way home before they've even made their first payment. Remember that your first motorcycle will be your "starter bike." There's about a 95% chance you'll drop it within the first few months of riding - it happens to all of us (I've been riding over 30 years and I've dropped every motorcycle I've owned except for my current one - knock wood!
)
Another recommendation from someone who's been there - stay away from 'boutique bikes' unless you want to spend a lot of money. When I dropped my 2001 Triumph Thunderbird and broke a headlight bracket, the replacement part was about $60 - if it had been a Honda it would have been about $15. BMW, Triumph, Ducati, Moto Guzzi and the like cater to customers with lots of disposable cash, and parts and service are priced accordingly.
Honestly I think a 650 is probably more bike than you need. A 250cc - 500cc dual sport thumper (1 cyl) or twin should be more than adequate for any beginning rider. Don't listen to the people who say "you'll outgrow a 250." Unless you're doing a lot of high speed road riding, that's just not true. Look around the world and you'll see that on most of the planet, a 250cc is considered a 'big bike' and people ride all over the place on 125cc - 200cc thumpers.
IMO 450cc - 500cc is the perfect size for a beginner bike in the US, unfortunately there aren't many bikes in that size category to choose from. The Suzuki DRZ-400, or an older DR-350SE (SE = electric starter) have plenty of power but not so much weight that they overwhelm you.
Scan Craigslist and Cycletrader for used bikes in your area, and if you have a friend who is knowledgeable about motorcycles, take that friend along to check out any bikes you are interested in. Unfortunately, this is the worst time of the year to buy a motorcycle (although it's the best time to
sell a motorcycle) because when the weather gets warm people get "bike fever."