What are the differences between an investment mortgage and a personal mortgage?
It's just a guess, as I'm from the UK and am unfamiliar with the term "investment" mortgage but is it one where you are buying the property in order to rent it out, and make money from it, rather than to live in? In the UK we call those "buy to let" mortgages and one of the main differences is that you have to have a higher deposit to get that type.