How to pull out equity?

[Andrew Magoun]

I currently have 9 units spread over three properties and am under contract for adding a duplex. All told, there is about $400k in equity built up between the three properties. I'd like to be able to tap into that. 

Here's the tricky part: All three properties have private loans with interest rates under 3% and very good terms. What's the best way to tap that equity without drastically increasing my borrowing costs? Is that even possible? Is it worth it to even try? Thanks in advance for the advice.