Also encourage you to read the interview with J.R. Vassar, "Calling and Seduction of the City." He is the planter of Apostles Church in Manhattan, NYC. I met him in my first year of ministry in Colorado when he spoke at a college retreat I organized. Good guy.
In other Redeemer resource news, I noticed a few days ago that Redeemer has a Coaching Urban Church Planters book out from J. Allen Thompson. Should be helpful.