There is no blanket federal law that prevents the private ownership of machine guns. Nor, in most states, is there any prohibition on law abiding citizens owning machine guns.
After you choose which firearm you want to invest in we will handle all the paperwork. The authorities will check that you don't have a record or are otherwise prohibited from owning such a weapon. Then, after a few weeks or months you will be approved. There is a single $200 one-time tax on your purchase and some reasonable rules to be followed while you own the weapon -- but that's it!
No inspections. No BATF visits. Just the enjoyment of your investment.