Honestly? Spend the money to have an attorney do it right. You will probably screw it up. I see it happen all the time. Look at the amount you are loaning. If you cannot spend 10-20% to hire someone who knows what they are doing, you shouldn't be loaning the money.
The key is not the wording of the agreement. What gives a mortgage its main effect is recording with county's recorders office. You have to give notice and put all other potential lienholders on notice that you have a mortgage.