Also are you wanting to do an 01 or 07? If 01, you're going to need demo letters for post samples. I contacted nearly every LE Dept in FL about this and out of the 5 or so that I got a response from, none were willing to give a letter. Although you can technically get one from anywhere in the country. If you are going 07, add another $2250 a year. As for doing NFA transfers just remember that a lot of the reason some local shops charge 75-100 to transfer is that the items take up space, and for a long time. The shop I know of that is linked with SS doesn't charge anything extra other than the $75. You'll have to do 7 NFA transfers to pay for the SOT.
Personally I'd look for cheap office space somewhere. You could get a commercial zoned office in the complex I used to be in for like $150 a month. This would save you the zoning variance fee, keep your home address from be listed as a "gun dealer" (possible target as people will assume where there's a dealer there's guns, you are in Jax after all), plus keep people (that you usually don't know before hand) from coming to your house.
If you decide to get into ordering or selling guns, you're going to be limited on distributors. There's a few that just require a FFL but other (and some larger ones) require a store front. Ellet Brothers is one of the bigger ones that comes to mind needing a store front. You likely won't be able to get the latest and greatest guns without dropping some serious coin. Not even the "latest" really. Glock 9mm guns this year have been tough to get for smaller dealers as they stay on allocation as of late.
It can defiantly be a nice supplement income but it's not all it's cracked out to be. Plus from experience, shooters regularly sells guns cheaper or close to the price you'll be able to buy them at dealer pricing. Depending on what side of town you are on I may be able to help push some transfers to you though in about 3 months.