Erika,
Let's take a deep breath, and a dose of cold, hard reality.
I know of NO reputable banking/business that would offer an unsecured 50K line of credit online and with no hassles.
You might find a guy named Vinny that would do it. Good Luck with him.
Your best bet is the bank you already do business with. Talk to their commercial loans department. They will tell you what you need, how to present it, and what kind of security they will require.
Be very careful of these loan offers, credit lines, grants, etc you see in the spam folder in your email. A little investigation could save you a LOT of money, time, and extreme headaches.
There's an old adage that comes to mind, 'If it sounds too good to be true, it probably is....'
Good Luck!
Source: http://www.abusinessmentor.com