Should I refinance my duplex

[Maricell Hall]

I originally purchased my duplex  for about 320K The current market will Appraise it for at least 600k-700K. Should I refinance? Should I take the maximum out? buy another property in another state? I wanted to hopefully finish the basement and turn it into a legal apartment. If I do this I can easily add an additional 2400-3000 a month. Currently my mortgage is 2250 this include property taxes,  insurance, water and electricity. Im currently collecting  4750. If I  refinance  the mortgage will jump to about 2700. Please help!