The main problem is in fact compound interest and how it balloons a loan over time. That is what makes compound interest so deadly, its extreme effects are not initially recognized by the average person and even if one knows about it, it is very difficult to get an intuitive understanding of it.
I have tried to get a small example of the OPs loan calculated and it looks pretty much on point with the values they gave us. It is actually 60K only for interest for a 120K loan, making interest 50% over the loan. Half of the loan is added on top! And that is with only 6% annual interest rate, compounded yearly.
Tldr: 6% APL generate compound interest amounting to HALF the original loan.
