Things have changed drastically from a few years ago when you could provide the lender with a rental contract on your first home (normally they would have to see months of the tenant paying through cancelled checks etc.) With the recent mortgage fraud, I don't know anyone who will take that risk. You probably would have to show a certain percentage of equity in your first home. Most people are having to qualify for both properties in order to purchase while renting. The only way to know if you qualify for certain is to speak to a loan officer and they can gather your information and see how much you would qualify for while still taking into consideration your first mortgage.
I would be more than happy to get you connected with a lender in North Carolina that can assist you in a pre-qualification. My email address is email@example.com . I would also be more than happy to start sending you listings that might interest you, so that when you decide to move you will have a good concept of the area and what area of Charlotte you would feel comfortable calling home.