Should I price the land 2 times above market value and offer a low interest rateORPrice the land at current market and use a very high rate?

You can still achieve it, but finding deals that actually pencil out on all criteria (low enough purchase price, low enough renovation cost, cash flows on the backend, all cash out at refinance) is pretty hard.

. - low vacancy.  

The median home price is also very low nationwide which creates a low barrier to entry.

You’re in a great position with a property that’s appreciated significantly, a low-interest mortgage, and clear goals to boost cash flow and transition into full-time investing.

I'm working with a company who owns a small, 19 unit, senior and low income apartment building.

This setup alone feels like a solid foundation for financial freedom.Here’s my dilemma:While I understand that my mortgage interest rate is very low (2.8%) and there are tax benefits to carrying the debt, I’m wondering if it might make more sense to aggressively pay off the loan.

Long-term wealth is it's superpower, and yes, you have a little cash flow to keep the lights on. 

This vary heavily town to town. 20% down is great if buying strictly as investment but if you have a way of owner occupying I would explore that route and apply the 20% down to increasing value of property and instead using low money down loan. 

So making it my primary is a low bar.