I agree with all the others. Take the MSF rider training courses in your state. Take beginner and advanced course 4 to 6 months apart so you'll have enough road miles experience to get full benefit from the advanced course. Taking the state-approved MSF beginner class can often be done at a discount in Oct-Feb because so few people take it then. Smaller class sizes too. And the MSF beginner course may pay for itself: Some insurance companies will give you a discount on your liability insurance and some states that require a motorcycle endorsement on your driver's license don't require you to do a road test if you've had the MSF beginner course. Here in Texas, that last item is huge because you're required to get your bike to the DMV without riding it (because you don't have a motorcycle license yet) and you have to provide a car and driver so the official grading the road test can follow you around while you're doing the road test.
As for you father's bike, it's like all the others said: It's like the difference between a powerful but docile horse vs an equally strong but skittish race horse that doesn't want to amble along at a slow trot. So I agree with the advice to buy a good used bike that you can get a year or so of experience on (call it 5,000-10,000 miles in various weather and riding conditions).
Look for a bike that looks like the owner took good care of it and take good care of it yourself to maintain its resale value. 200-300 cc is big enough since you're going to resell it after you have enough experience to ride your father's bike. My Honda Rebel 250 goes from 0-65 plenty fast enough for around town riding and bikes that size are often available used because many riders move up to a bigger bike after a couple of years. Avoid bikes of whatever size that look like a crotch rocket if you can. They're more likely to have been abused by the previous owner pushing the bike too hard while trying to show everybody how fast he is. Also, if possible, avoid bikes where the seat is so high that you can't put both feet, or at least the toes of both feet, on the ground at the same time. Having to slide your butt way over and stretch to put your foot on the ground at a traffic light gets old real quick.
If you feel up to it, do as much of your own maintenance as you can on your starter bike. At the very least learn how to adjust the chain, adjust the brakes, change the oil, change spark plugs and that sort of thing. If you make a mistake, you want it to happen on the starter bike, not your father's pride and joy.
Speaking of which, motorcycles don't like being left idle for a long time. So crank up your father's bike now and then to keep the innards lubricated. Roll it back and forth in your garage and mash the brake levers a few times to keep everything loose and lubricated. Maybe add Sta-bil fuel stabilizer to a full tank of fresh gas. Hook a low-power motorcycle battery charger to it every so often to keep the battery charged, but don't over do it.
Now for my own "been there done that" newbie story. It was a nice but overcast day and I was on a 45 mph four lane street. It started to sprinkle, but not enough to be annoying. A few minutes later I got caught by a red traffic light. After coming to a gentle stop on the right hand side of my lane I put my left foot down and promptly fell over. That gentle drizzle mixing with the oil in the center of that lane had made it so slick I didn't have time enough to react to my foot sliding and I was too far off balance to keep from falling over even if I'd had more time to react. There's nothing quite like falling over while standing still, especially in front of a bunch of car drivers.
