Salary
Average Salary: $40,000
Expected Lifetime Earnings: $1,669,920
The amount of cash that rare book dealers make varies wildly—like really wildly. You might end up being that dealer who hangs out in his dusty, book-crammed apartment all day, eating SpaghettiOs to survive; or you might end up rolling in the dough, taking nightly champagne baths for fun. (We wouldn't recommend champagne baths; they're kinda sticky.)
The best salary estimate we can give is $40,720 per year, but that's just an average—you could make a bundle more or a whole lot less than that (source).
Let's check out a best-case scenario first. Say you happen to find a copy of Caxton's Chaucer (the first book printed in England) for five bucks at a garage sale, and then you turn around and sell it for seven million. Boom. Let the champagne baths ensue. The vast majority of book dealers aren't that lucky though (read: nobody has ever been that lucky, ever). This business is all about the long game.
You might buy a first edition of The Hobbit for $50,000. You could sit on it for ten years and sell it for $125,000. So that's $75,000 more than you paid for the thing, but you had to be patient to make it happen. If you manage to stagger your sales and purchases in the right way, you might make a sale like this once a year.
If your catalogue of books is full of dusty stuff nobody wants, though, you may never make anywhere near this much money. The truth is you'd probably make more cash investing in a basic index fund, but if books are your thing, it probably just doesn't have the same allure.
In order to make a living as a rare book dealer, you'll need to make regular smaller sales too. Your online catalogue (which is totally necessary these days) will most likely have plenty of items for under $100 in addition to the more expensive titles. When you factor in the costs to pack and ship the book, you might only end up making twenty or thirty bucks from a sale.
Even though those types of sales won't make you an instant millionaire, they may be what keep you eating ramen until the next big score.