A new peer-to-peer lending Web site from the founder of E-LOAN might give mortgage lenders more cause for concern when approving borrowers. Prosper.com allows users to easily borrow thousands of dollars from other everyday Joes, and early transactions suggest the site may encroach on mortgage lending. On the site, borrowers list the amount of money they want, up to $25,000, and the top interest rate they are willing to pay. Other users on the site…