There are a few threads on here where you can view valid collateral.  You can use those threads for guidance, but do not hold to them.  Valid collateral is anything you can quickly sell and recover your lent money back if the borrower does not pay.  As others have said, you need someone else to act as your escrow.  For small transactions I will act as your escrow if you want.  I charge no fee and only accept donations.  I currently also run a loan service and I hold my own escrow, but I have been lending for a short time now.  My Trust is not up because I do not ask for it when I loan and all.  It is frowned upon to openly ask for trust or do trades for trust.  I do the loan service to make more BTC, that is all.  Trust will come over time.  What ever you do - DO NOT buy an account to start doing loans.  People will still treat you as a newbie and you may end up with (-) trust.  Build up who you are with your account. 

Good luck and please ask if you have any questions.