cover letter, send it to the General Sales Manager at whatever radio station you are interested in working for. It always helps to stand out. Thats why I would suggest sending it in the USPS Flat Rate Priority Mailer (they look more important than regular letters) or even by Fed Ex if you can spare the expense. Make SURE you follow up by phone a week after you send it. If you wind up in voice-mail hell, keep trying. Persistent people make their own breaks.
Dont limit yourself to one radio station just because you happen to like the music they play. Youre not there to listen and it doesnt really matter what format the station is. If you want to sell, then be ready to sell whatever product is available Rock, Talk, Urban, etc. Professional Account Executives should be willing and able to sell commercials, remote appearances, and any kind of product inventory for any kind of format.
Thats what a professional does.
Now, as far as what youll make, as in any sales-oriented position this is really up to you. Most stations will start you off on a salary draw until you get yourself to a point where your sales commissions are providing higher income than your draw. From there, its up to you how much money you make. Motivated Account Executives can do very well.
Let me put it this way: where I work at a cluster of several stations one of the top Account Executives is driving a brand new yellow Corvette. Id say shes doing pretty well.
Good luck and make it happen!