Do you really know guns? Or do you think you do?
Go work in a shop for 6-12 months and learn the business somewhat.
First, location location location. Are there customers? Do they have $$$? Local climate for gun business. Cali? HA! SE US, maybe.
Second, Competition. A shop between WalMart and Bass Pro isn't a good idea.
Figure making no money for yourself the first 12-18 months. Few, if any employees. No benefits. All $$ goes back into shop.
Couple of thousand for startup costs- legal, accounting, phone svc, credit card svc, internet, utility deposits etc
Monthly expenses. Rent, phone, internet, health insurance for you, liability insurance, yellow pages, advertising etc
Finally, inventory. You gotta pretty much buy it. But it has worth and this is where bank loans may come into play. Go for your locally owned bank, not Bank of America or other biggie. Get an account there BEFORE you go begging for money. How is your credit. Unless perfect, good luck. Work on making it perfect.
Figure avg cost of $500 per item. Maybe more, maybe less, but that is a starting point. 50K is only 100 or so guns.
A bunch of C&R will make your shop look bigger and better for "low" cost.
Ammo- gotta carry a lot of stuff.
Stuff- this is where you can make some $$
How good a salesman are you? Your key to to making a living is being able to sell a soft case, couple boxes of ammo, ear muffs, and a cleaning kit to the newbie that buys a 10/22.
Don't fall in love with your inventory. That is for later when you can afford it. Everything is for sale.