I think, yes I am bias but, to get what is called an 80% AR15 lower made by Ares Armor for $55.00.  Or even a 80% gun kit mailed to you for less then $700.00 and you just need to finish the lower and off you go.
Ignore the $80.00 in the picture, uspatriotarmory.com has a better price. 

www.uspatriotarmory.com