But higher tax rate in PG county. 

If the answer is yes, then it's a no brainer to make minimum payments on your 2.8% interest rate mortgage, and use the funds that you would have paid extra to pay it down faster, to either invest in more real estate, the market, or anywhere else where you can get a ROI > 2.8%.If the answer is no, then feel free to aggressively pay it down as fast as possible, to become debt-free faster, and just have a large amount of money in savings or to splurge with.The bottom line is that your 2.8% mortgage is GOOD debt.

Quote from @Sean Kirk: I'm seeing what seems to be 10%+ cap rates on roofstock.

My first mortgage was almost 11% and that was a good rate.

What is the rate of your HELOC you have going and what would be your rate on the new HELOC?

Rates will range from Prime (currently at 7.5%) to Prime + 4% (11.5%).

That worked well when rates were 3.5% but that "strategy" no longer exists.

Working to figure out which route has the best conversion rates when targeting specific neighborhoods.

Plus I recently got a brand new calculator, wanted to see what out of state investors though the most important aspects of deciding between to similar rates cap rates in 2 varied size apartment. 

Many of these lenders allowing 2nds behind them are more expensive capital (10's - 13's in our current market [high rates - but now showing signs of coming down]).