Before you go and buy landscape nursery black pines, you should know you are getting yourself into a lot of work for these guys. Brent Walston had some excellent articles discussing Black Pines on his blog, and specifically this article:
Raw Material: Pines, September 2005
http://bonsainurseryman.typepad.com/bonsainurseryman/
It is well worth reading before you decide you want to purchase landscape trees for bonsai. While pre-trained black pines from a bonsai nursery are a far more expensive, they could save you years in development over landscape pines.