I have a home-based FFL. I wrote this up based on my experience getting it a couple of years ago.
Steps to getting a home-based Federal Firearms License (FFL):
1) Check your local zoning ordinances and HOA CCR's, if any. If either document prohibits you from obtaining a business license at your residence, go no further. The ATF will not issue you an FFL until you get a waiver from your county and/or HOA.
2) Check with your homeowner's insurance to see how much it will go up if you run a firearm business out of your home. Hopefully you have a local agent who you've personally known and worked with for many years, as the flunkie on the toll-free call center phone will probably freak at your questions. You may find the increase in premium alone makes getting an FFL unviable.
3) Another question for yourself - are you comfortable filing federal and state tax returns every quarter, and monthly sales tax returns? If not, add CPA services to your list of expenses.
4) If you've gotten to this point, find an attorney to help you form a S Corp, C Corp, or LLC (most folks go with an LLC). This is not the time to go with a DIY document off the internet, especially if you plan on dealing in NFA toys. Besides, being in the firearms biz, you're going to need an attorney sooner or later anyway; might as well get to know one now.
5) Once your corp/LLC is formed, get your EIN and obtain any necessary state and local business licenses to run a business. If you don't have these, the ATF will not issue an FFL. See #1 (and yes, they go to your county or city courthouse and check).
6) Call the ATF Distribution Center (703-455-7801) and ask for an application packet. It will include several copies of the application (no carbons unfortunately), fingerprint cards, and instructions.
Note that all manufacturers (Type 06, 07, and 10 FFL's) must register with the Department of State and pay ITAR annually. This registration fee is $2250.00.
A Type 01 (Dealer) FFL is $150 for the first 3 years, and $90 every three years afterward to renew the license afterward.
ETA: Some states, such as NY and NC, have additional licensing requirements & fees for gun dealers.
Also, avoid the "we will help you get your FFL" companies that want to charge a fee to get you your license. Everything you need is available free from the ATF.