Hi, I am just starting a similar league on Yahoo! and our plan is to have limited (4-5) minor league slots, which you can fill once a year in a draft. When they are called up, you may add them, provided you make room on your active roster. You may also keep them on the minor league roster until the end of the year. Once they no longer qualify as a minor leaguer, however, you must promote them or drop them before the next season begins.
How many slots does each team have in your league?
Thanks, and good luck.