Yeah, once you pay the very high price for a machinegun that was registered here in the USA before the cut off date in 1986, everything else is pretty much the same as owning any other kind of NFA weapon.
Except, if I recall correctly, for silencers. I heard you don't have to notify the feds and fill out a form before taking your silencer out of state, but you DO have to do that for NFA guns. (Just in case you want to participate in the Knob Creek M.G. shoot one day!)
You can get a Cobray / MAC / RBP type ugly little bullet hose (think, machine pistol with a cheap folding stock) for about $3500. They're really common. All the manufacturers of those kind of guns cranked up production of frames in 1985 and early 1986, and got them registered, and completed the guns later. The M11/9 is something you can modify with different uppers, different calibers, different stocks, and you can modify it to take drum magazines instead of the standard 30 round stick mag.