I had an FFL for over 20 years and finally gave it up 2 years ago.
First don't let the guys scare you about enhancing your collection. I asked the compliance agents numerous times over the years how many guns you have to sell to be considered "in the business". They won't tell you because it has never been defined. One year I sold one gun, though I bought several. No problem.
A problem with FFL's is that you sign the form saying you will comply with all laws, ordinances etc. This means zoning laws, sales tax collection, filing DBA's, tax laws, gun lock laws, storage of firearms laws etc. It is a federal crime if you don't meet every law. It just gets to be a hassle after awhile. It is a pain in the ass sitting down each year to do your taxes and having to figure out what percentage of your house, vehicle and such is "business related" when in fact your biz is a shell so you can buy guns cheaper.
If you think you will save money with an FFL, I have to warn you.? You will buy 10 times as many guns as you normally would just because you can.
If you are serious about going into business consider that is a cutthroat industry. During the 1980's I doubled my yearly income just doing gunshows one weekend a month. Gunshows are not a very good source anymore. Too much junk, too much bad press, too much competition.
I never liked it when someone asked me to "find" them such or such a gun, and after spending a hell of a lot of time searching the internet and numerous distributors for a week bitched about the price because a friend bought it $10 cheaper at a gun show last year. Another one is that someone will order a cheap POS gun and then complain when it doesn't work or they don't like the way it looks and wants you to take it back.
My suggestion is get a Curio & Relics license. This will get you discounts on C&R guns and accessories and stuff but doesn't have the same amount of paperwork or responsibility. Second, hook up with a dealer that will do transfers for you for a reasonable fee. Some dealers are happy to take a fee if they don't have to do any work.
Good luck.