THEN ALLOT OF TIME AND HARD HARD WORKLIKE ANY BUSINESS REAL ESTATE INVESTING REQUIRES KNOWLEDGE, INTELLIGENCE, IMAGINATION, DEDICATION, DEVOTION, FORTITUDE, PERSISTENCE, AND A LITTLE OR ALLOT OF LUCK  AS WELL AS ALLOT OF EFFORT AND YES SOONER OR LATER MONEY AND ENOUGH MONEY OTHERWISE YOU JUST ARE NOT GOING TO LAST. 

Your mortgage was almost certainly not compound interest, it was simple interest; I'm not even sure if compound interest mortgages are legal in any state in the US.I realize it's uncomfortable to have your world view challenged, and I applaud you for the financial fortitude to pay off your mortgage.