Forget about getting a 600 or 750 to start. For $4500, you should plan on getting everything you need - and that is not just the bike. You will want to go to the MSF course ($250), and then you will want to buy gear. A helmet, jacket, gloves, boots, and pants will add up when you figure that in reality, that means multiples. You will probably have a mesh and a leather jacket, as well as Draggin Jeans and leathers. Plan for these costs as gear isn't cheap, but is just as necessary as the bike.
That will eat into you cash flow that is available for your bike.
Don't worry about the looks of your first bike as much as mechanical condition. YOu will probably drop your first bike (most do), and scratches are inevitable.
For a first bike, you want something easy to control and comfortable. Look into SV650s and older 600s to start. When you decide to get a bigger bike, you can resell these and not lose a lot of value.