Building Business Credit Help

[LISA F.]

Hi Everyone,
This is my situation.
I have 3 (3) families properties in New York City. One of the buildings which I reside in is in my name and the other 2 I transferred into a LLC about 3 years ago so i have 3 mortgages on my personally credit history.
I'm looking to build up business credit to help me down the road purchase my next building. Should I use my current LLC to start obtaining business credit or open a new one? My next purchase I want to have in a new LLC not in my name or the current LLC.
All feedback and help would be much appreciated.
Also I manage the buildings through my own property management company which is just a DBA. Does anyone have some suggestions? :D