How to get money out of current property to invest?

[Dave Mai]

Hello to all biggerpockets!

Long time listener, first time posting.

I bought a duplex about 3 months ago for 430k. It’s under the market price. I put in 20% down payment. I know the property worth about 500k- 520k.  I have about 40k for investment. I am looking at other properties with lots potential.
how can I get more money out of my current duplex to down payment for another duplex?

I need to rise more capital. Any advise?!? 
please share what you think!

Thank you!