I got my series 1 in 1965 (They call it a series 7 now) - was a broker b4 mayday changed commissions from fixed to variable. Got "promoted" to manager of Options trading in 1973 (our firm was the first firm to buy a CBOE seat). Starting in 1975 I also headed OTC market making for a strong Regional firm. Stayed in that position till 1983. In that position I got to really see how brokers operate. In those days all orders went through the trading desk and OTC 'mark-ups' (read commissions) were usually set by the broker - not the firm, even though the firm 'made the market'..
Believe me, I can tell you everything you want to know about brokers. I can also tell you - you don't want to be one. Sure, there are a lot of honest, smart guys and gals in the buisiness, but, there are a lot that do not belong in the business.
Unless you are really well 'connected' (read - know a lot of poeple with a lot of money), you will fail.
In todays world, most brokers are glorified "asset gatherers". They spend all their time dialing and smiling, generally do not know very much about markets, stocks, interest rates, economy etc.
I do not know the success rate but I would bet 20-1 that 75% do not make it past year 3.
Good luck on whatever you decide, Wayne