Things I've learned over 50 years of collecting. Boy, this will make a lot of friends.
Rule #1 -- Spend your time before you spend your money. Read, listen, watch the action at shows and know, for yourself, what you are buying before you ever lay money down for a gun. Know what's hot and what's not.
Rule #2 -- It is a rare man, indeed, who buys a gun from a dealer and flips it in short order for a profit. Dealers will hype you that "guns have been a great ride financially" and, for them, they often have been. That's because they are hucksters---buyers and sellers-- and they make their money on the spread. The bigger the spread, the bigger the profit.
Rule #3 -- The real money is made when you buy a gun, not when you sell it. That is, the price that you can get for it is, for the most part, fixed by the marketplace. I've seen dealers with a following and/or with the gift of gab who can sell an ice cube to an Eskimo, but, on average, a dealer knows that he will ultimately fetch what the laws of supply and demand will permit, no more. So, to make money, you need to think and buy like a dealer...I'm talking pennies on the dollar. The corrolary is pure and simple. If you pay retail, you had better really like it. Sure, dealers sometimes trade among themselves for more than pennies on the dollar, or when they have a sucker waiting for your piece, but they get their "big licks" when they ambush an ignorant seller.
Rule #4 -- If you knew how much restoration a substantial percentage of "original" Kentucky rifles have had, you would cringe and perhaps be in immediate need of smelling salts. Hence, buying a gun sight unseen is a very, very risky business. I unequivocally recommend against it. Let the buyer beware. Is a rifle with new wood from the wrist on out what you are looking for? Barrel been stretched, too? Most original flints are not...well, I'll stop there.
Rule #5 -- When hucksters tell you that they don't know, they probably do. When they tell you they do know, they may not. Unless they are thinking of you as a long term customer, they aren't thinking of you at all. You, the buyer of old guns, must have enough confidence in yourself, to make buying decisions based upon your own opinion, and then, and only then, do I seek an outside opinion, other than mine and the dealers.
I live in the heart of central PA. Around here general antique shops yield almost nothing good. If they do, it's way overpriced and there's no room left for you or me. Gun shows are occasionally good places, if you are willing to pay the going rate and you know the dealer to be one of the reputable ones.
Best bets: find some rust and splinters at yard sales, deal with museums that are deaccessioning items, put out feelers at work and among friends. Learn how to rebuild them and be a player in the middle. Buy low, rebuild and sell to dealers at 60% retail, give or take. In time, you'll sell it. Sell two and keep 1; that's your retirement. You can do this! You just have to learn and have confidence in yourself.