Mortgage and lein for a large purchase

[Calvin Thomas]

I am looking at a large complex to purchase in NY, however, I am unsure on the best way to purchase.  It's about 3m, and a 20% deposit (or more, rather place less) would be in my current assets.  I have several multi-family homes owned outright.  Is there anyway to use the equity in my current buildings for downpayment?  If not, what is the best way to acquire said property?  The CF is nearly 750k a year, so the complex will pay for itself.  Never gone through the mortgage process, as I've always paid cash.  

Ideas?  Suggestions on how to proceed?