I have been doing some research on purchasing my first ar-15 and after lots of questions and a few gun shows I still have not bought one. So, I have come to this forum to ask a few questions on purchasing parts to build one.
If I buy a complete lower and upper is this all I need?
What is all involved for a basic build?
Is it cost effective to do this versus buying a new unit.

yes--a complete lower and upper are all you need--just snap in the pins...

build--check up top on the tacked thread: www.ar15.com/forums/topic.html?b=3&f=4&t=226782

building is more cost effective if: you plan on building more than 1; if you want to do future customization/accessory buildups

overall, building your own AR is not only a great expeience and gives you something to do, but it will save you $$$s in the long run--sort of--b/c you will end up spending said saved cash on more AR stuff

I would buy all the parts and do it yourself. There's nothing more satisfying than shooting something you assembled.
Get everything and if you have problems the guys in here are great about helping.