are there any cost involved with building a ar-15, other than parts and shipping, does it cost to register and file paper work, etc.

The only part that needs to ship to a FFL is the lower receiver.  To receive it from your FFL you will need to fill out the required federal paperwork.  All other parts can ship directly to your house.  Besides actual parts, you may need some tools to complete the job, depending on how much you want to "build" yourself.  Complete upppers can be purchased, or bought in parts.  Good luck.

Like Szurgot said, it really depends on how much you want to build the rifle.  If you get a complete upper and a complete lower all you have to do is snap it together basically.  If you get a stripped upper and stripped lower, there is going to be more building involved.

But on the plus side is the experance that you will gaine. Its like the diferance between driveing a car and being able to rebuild the engine. Plus it allows you to build the gun you want (barrel lenth, upper type, stock etc.) that you want not  just what they have for sale at the local gun shop. My two cents.