Complete AR-15 kit from Slickguns/Brownells for $404

[junior125]

I have a PSA PA-10 that I just built, haven't gotten out to shoot it yet

[AD]

Yes they are legit.

[Concerned Dad]

Is that everything I need to build an AR?

[AD]

You also need a lower receiver. That's the part with the serial number on it that gets registered. If you are in a state like AZ you can buy any firearm in a private sale with no paperwork. You can get papered one for ~$60-120 depending on what you get.

http://palmettostatearmory.com/index.php/catalog/product/view/id/1996/category/4282/

If you can do a private sale they can be had from $100-300. YMMV

You can buy a 80% lower and finish it yourself but it might still be track able via shipping records.

There are videos on Brownells that take you through the,process step by step.