If you are interested in becoming a breeder, I would find a breeder to mentor under. GSDs are incredibly complicated dogs, and the lines and genetics are intricate.
My GSD breeder friend (now retired) spent decades learning about lines, percentages, rearing, anatomy, genetics, temperament and its fluidity, learning stages, on and on and ON. She bred for thirty years, and she could list offhand what lines matched hers, what genetic faults were present in her lines (ALL lines have SOME faults that pop up, ALL lines, period), what lines would correct what problems but at what cost.
Some breeders will offer co-ownership, and if I was seriously interested in 'trying out' breeding, that is the direction I would look. That said, most breeders are very VERY picky about who they will co-own with--as they should be. Most won't do it at all.
But, if I decided I wanted to, that is how I would approach it. Mentor under someone with forty years experience, get their advice, follow their advice, etc. (I hasten to add that the co-ownership contracts that I know of involve the co-owner keeping an adult bitch and one pup from the litter. Not, you know, making any kind of profit. Certainly not deciding on the stud or bitch--maybe helping to decide, but not deciding entirely.)