In an extremely low interest rate environment, likely the lowest in history, now is the time to tackle all those debts with more of your payments going towards principal then ever. It surprises me to read the headlines about ballooning consumer debt, people empowered to gorge on more and more debt, right up to the max of their capabilities to repay. Seemingly expecting that the party will never end.
As you described your situation, it seems as though you run the risk of buying something that you might not otherwise, in order to capitalize on the current low rates.
Obviously, pay the 9.33% first. That's a guaranteed 9.33% ROI, no tenants, no asbestos, no mold, no surprises. That is quite an exciting and ambitious goal to have 15 units, I wish you best of luck!!! Your hands are going to be full.
There is a lot of anecdotal evidence corresponding falling interest rates with swelling real estate prices. It stands to reason that as the rates start to creep up, people will be heading for the exits and the demand for these places will be lower, giving you more chances to look for deals.
Keep in mind that it is highly unlikely that rates are going to skyrocket as that will send shock waves through the entire economic system. Instead, expect slow, gradual, methodical increases over the next few years, (most of what I have read is stating 0.25% increases per quarter) lots of time to ensure the right opportunity is there.