01 FFL is dealer. 01 dealer in machineguns/NFA is Class 3 SOT.
07 FFL is manufacturer. 07 mfg of machineguns/NFA is Class 2 SOT.
Machineguns and silencers, etc, aren't really "C3" - that just refers to a dealer in NFA (Title 2) weapons. However, most people and many dealers incorrectly call machineguns "Class 3", so you can get away with it as common usage.
You don't have to have a commercial storefront - you just have to comply with local and state zoning laws and business regulations. If unzoned, or zoned commercial, or you get a variance, you can do the FFL from your home or garage.
morlock13: 01/07 FFL dealers without the Class 3 SOT are just like regular joes when it comes to NFA items - they still need CLEO signoff, fingerprints, photos, $200 tax, etc. The only difference is that they can receive them directly from out of state, without going through an in-state C3/C2 first. To be a C2/C3 is $500/yr minimum ($1000/yr if your sales volume is over $500,000 gross).