At your size, you’ll have no problem handling a first motorcycle up to 350 lbs, and 650cc, though you should probably stay away from the 600cc fourbanger sports bikes, as they are quite wide, and have narrow handlebars, which can inhibit newer riders in parking lot riding.
First off, $3200 is a high price for a Rebel. The Rebel has stayed the same since its original release in the mid-eighties, and is a very low-powered, stone simple bike. You could get a used one for 1/3 of that price. Additionally, at your weight, the Rebel will feel very underpowered, I’m afraid.
If you like that type of bike (cruiser), I would recommend a mid to late-nineties Honda Shadow VLX 600. It is a 583cc v-twin with attractive styling and low weight. A friend of mine just picked up a 1996 with 6,000 miles in perfect shape for $1700. The Yamaha XV535 from the mid-nineties is another option in this category.
If you’re not particularly enamored with the cruiser styling, but like more standard bikes, I think you ought to check out the Suzuki SV650 v-twin, which is pretty light, and very narrow, which makes it easier to handle in low-speed chores like parking and backing up. It retails for $5699, but you ought to be able to find a lightly-used 2000 for under $4000. A similar, but lower-powered bike is the Suzuki GS 500.
You might also consider a dual-purpose bike, if these fit your style. I would have no fear sending a beginner out on a Kawasaki KLR650 or better yet a Suzuki DR-Z 400. Both of these bikes are suitable for riding on the street and little jaunts down dirt roads. The KLR can even be pressed into service as a touring bike, if you’ve got a desire for longer trips. Dual-sport bikes are also lovely to learn to ride on, because they have wide bars that make steering and low speed handling very easy, and have narrow profiles.
I think your idea of starting with a smaller bike is a good idea, generally, but a 250cc bike will be underpowered for you, which will make highway driving and longer rides a real drag. You’ll be fine with a larger bike.
Do be sure to take an MSF Basic RiderCourse, and purchase proper protective gear, including real boots. Just post a reply if you want specific recommendations.
My brother is 20, and just learning to ride. He is 6’2" and 155lbs, and has no trouble riding my KTM Adventure, which weighs 340lbs (and has a 37" seat height!). He’s taken the MSF Basic RiderCourse, but his experience prior to that was limited to a 50cc moped…
KTM 640 Adventure
Honda CBR1000F