Buying a new gun is a loser from the word go. Unless you have a time machine to take you back maybe 50 or more years. You've got to guess correctly and then hold for 50 years. Not easy.
If you invest in anything, gold, silver, stocks, land, you've got to be know all about your subject. With guns its no different. Its easy to get skinned buying a used gun, but its where the better opportunities lie. If you want to increase your knowledge, buy Supica and Nahas (3rd ed) and then read it end to end a few dozen times.
Then read the posts here in the older revolvers section.
I have friends who don't base their purchases on knowing about the rarity of a gun, they go on condition only. They won't buy a gun with even a speck on it. Either way, you won't make any money buying and selling (like a day trader). You've got to buy wisely and then hold. Some people do buy a gun, up the price and make $50 at a gun show. Besides being close to the edge of illegality, I don't know what it accomplishes. I do sell guns out of my collection, but usually because my collecting interests change or because I've bought a better example.
Making money is pretty difficult. The income tax folks will tell you that you need to declare your winnings on your tax forms (and pay tax).