is btcjam is trusted?
Personally, i've never taken a loan in my life... I've had some coins invested in btcjam, and i must say i've not ROI'd (was able to withdraw less than i put in due to loan defaulters).
But: i'm pretty sure that, so far, btcjam itself is not cheating... Just the borrowers on the site have a habit of ripping people off lately (or i might have an unlucky streak)
With 15% interest it would be cheaper to go to a bank instead. It's easier and more convenient for bot of you. Remember you are just a Jr. member. It needs trust to give out money.
And finding a 5-7k collateral will be ard.