Advice on my third property

[Andy Mejia]

Greetings all, 

So me and my mother own our primary residence where we have a little under 220k due on the mortgage with an unnoficialy appraised value at 719k. The monthly payments are 2300 with an interest rate of about 6.2% (this was around 2008 and my mom made all the decisions at that point since i was so young). I am wondering how much money I should take out for my next investment as that will be my new primary residence. I live in NYC so the prices are pretty high but I want to live in a good location and rent out where we currently live in. I obviously have a lot of equity and I was wondering how the math would play out if we used average interest rates on the current mortgage. Ex. Currently we pay 2300 a month, its a multi family home (2 apts) with a basement. I want to know if i take out 300k how much would I be paying monthly and If I should even take that much out or even more. I have never done a refi so please excuse the ignorance.

Thanks,