You need to sell some firearms in order to keep your ffl in not the ATF sees no reason for you to have one. This is of course if the ATF "grants" you the license in the first place. You can not get an FFL just for personal reasons. It is to get into the business of selling firearms. The one you can more easily get is the "collector of Curio and Relic" C&R FFL.
A Class 3 SOT dealer is a dealer of NFA firearms
A Class 2 SOT manufacturer is a manufacturer of NFA firearms
A Class 1 SOT importer is an importer of NFA firearms
Type 1 FFL is a Title 1 dealer or gunsmith
Type 2 FFL is a Title 1 dealer doing business as a pawnbroker
Type 3 FFL is a licensed collector of Curio & Relic (C&R) firearms
Type 6 FFL is a licensed maker of ammunition and reloading components other than Armor Piercing ammunition
Type 7 FFL is a Title 1 manufacturer of firearms, ammunition and ammunition components other than NFA, Destructive Devices and Armor Piercing ammunition
Type 8 FFL is an importer of Title 1 firearms and ammunition
Type 9 FFL is a dealer in Title 1 firearms including NFA destructive devices, but no other NFA
Type 10 FFL is a manufacturer of Title 1 firearms, ammunition and ammunition components, including NFA Destructive Devices but no other NFA, and not including Armor Piercing ammunition
Type 11 FFL is an importer of Title 1 firearms, ammunition and NFA Destructive Devices, but no other NFA
To get a Class 3 SOT status, you need a dealer or manufacturer FFL which includes Type 1, 2, 7, 8, 9, 10 or 11 - and pay a yearly $500 tax due every July 1st.
To get a Class 2 SOT status, you need a manufacturer FFL, which includes Type 7, 10 - and pay a yearly $1000 or $500 (reduced rate for small manufacturers) tax due every July 1st.
To get a Class 1 SOT status, you need an importer FFL, which includes Type 8, 11- and pay a yearly $1000 or $500 (reduced rate for small importers) tax due every July 1st.