Div 7A Loan Agreements that go for 25 years

Question: I can do 7 year Brett Davies Lawyers’ Division 7A Loan Agreements at www.lawcentral.com.au. However, I need to pay back 1/7 of the capital each year. I want to do a secured Div 7A and therefore, reduce the capital to only 1/25 of the capital each year. I understand this is a Mortgage which Brett Davies Lawyers has to prepare (rather than go through the Law Central website). What is the difference between the standard unsecured loan and the Div 7A Mortgage?