Hello Tbell40
Firstly i assume you have a permit to grow, and that you understand the risks of growing...
... Now thats out the way, Where are you going to be growing? (Closet, Big room, Small room, Are you building your own cabinet, Are you buying a tent?)... If you do know please tell us so we can help you more and also include the size of your grow area (length x Width)
... A 400w should be good for about 3x3 feet, 4x4 feet max... What method do you want to use? (SOG,SCROG,Straight up.. BLAH,BLAH)... What are you going to be growing in (That is the growing medium.. eg. Soil)
Thank you
James!