I am a dealer. I can tell you that Sel 691 gave some of the best advice. Work for one of the larger auction houses, or a company lke Littleton.
Before that though you need a lot of education. I mean ALOT. I have degrees in Aerospace Engineering, Mathamatics, and Satelitte Communications. I will tell you truthfully that I have way more time involved in learning my trade as a coin dealer than anything else.
You need to learn to speak coins. You NEED a basic understanding of the Indian and
Lincoln Cent series; Buffalo and
Jefferson nickel series; Barber, Mercury, and
Roosevelt dime series; Barber, SLQ and Washington series quarters; Barber, WLH, Franklin and
Kennedy halves; Trade, Morgan, and
Peace dollars. Classic Commem's. You need to be able to tell what a full head SLQ, and a full thumb WLH...and which ones, if any, are common. For instance Full Split band Mercs give you a premium. Sometimes a huge premium. Unless they are late 30s to 45 coins issued at Denver which was well known for it's tight spacing and not running a die till it was dead...in all it's issues. And Grading, grading, grading!
Consider those your equivelant to your Freshman and Sophmore years at University. Except it will take you much longer, unless you develope your education in coins to the detriment of your college studies.
Jr and Sr years; Snow numbers, VAMs ( which can take years to learn), Proof characteristics for early
LWC and
Peace dollars. Full steps, Full Bells, and more Grading, grading grading!
Graduate course. Early Coppers, which should be a whole "year" by itself. CB and
Seated coinage and their varities. Sheild Nickels and varieties. Colonial Coinage. Patterns.
You need to understand the bullion market and more importantly how and when to cut your losses so that you can have cash flow; which you should also understand.
I am a fifth Generation Coin Collector, and a third gen dealer. I have been involved with this since 1965, and I am still learning new stuff, almost on a daily basis.
I'm not trying to dissuade you. WE need new blood. What I am saying is that this is not as easy as it looks. I make a lot of money...one more time...a lot of money on other dealers who simply do not understand varieties.
Good luck