Nice compact AR15 pistol for less than $500:
Upper with KAK flash can - $240 - http://palmettostatearmory.com/psa-...-can-no-bcg-or-charging-handle-516445150.html
Pistol Magpul lower - $140 - http://palmettostatearmory.com/psa-complete-moe-pistol-lower-receiver-black.html
BCG/CH - $90 - http://palmettostatearmory.com/psa-...-7075-t6-forged-mil-spec-charging-handle.html
Cheap ($8.5) to free shipping then $15 for FFL fee = less than $500. Good deal IMO.
Then just submit SBR paperwork and $200 and 8 months later you can put on a proper rifle stock. Beautiful.