About to pay off duplex - next steps?

[Mike DeLong]

Later this year I will pay off my first investment property - a duplex that brings in ~$1,100 p/mo and has a market value of ~$120K. The property is located in a solid area of Charlotte, NC. Knowing I want to pull the trigger on my next investment after it is paid off I'm looking for feedback on what that investment could be and how I can leverage a paid off property towards it (without selling it). Any thoughts? My background is in residential but have been learning about the commercial side as well. Thanks all.