As for league rules, yet we try to keep them somewhat simple, everyone can just see Buzzerbeater official rules and you'll notice it contains multiple pages of worth information (and actually lacks many unwritten nuances, that I've had to hunt from the forums, which I've found very unhandy and unnecessarily difficult in many cases). And as many basic rules of BB leagues can be applied to homegrown league, not everything needs to be written from zero so to speak.
But as far as an original definition of homegrown team goes (which is applied to this forthcoming homegrown teams league as well) it is technically also possible having bought back your own draftee and still be counted as a homegrown team.
This, in some way could create situations in where a teams "salary rating" has been raised by hundreds of thousands of dollars by purchasing back players that he/she has sold before when they had a lower salary. I do not mention this following suggestion because I'd think we'd need to exclude such teams from the homegrown league; I still think we can and should welcome such teams.
However, having said that, there is of course a questionable side in this, as some purists would say. I think if you've gained more salary by purchasing back your own draftees (selling when salary was lower than when you purchased them back), then for the sake of openness and fairness I think we could/should make some kind of compilation/table/information page of all teams together (in one table) into which we sum up some essential information such as certain team wages (for instance top 8 or top 12 players salaries), and into that table add for example following symbols:
+++++ = team has never purchased any players
++++ = team has never purchased other players than their own draftees and has not gained a current salary advantage with such purchases
+++ = team has never purchased other players than their own draftees and/or players of their teams nationality
++ = team has purchased players before, but is now fully homegrown (as per Eliocroca CB's manager LOPO_s' original definition - or we could add a link to MrJs' article too) and has not received a current salary benefit by buying own draftees back
+ = team has purchased players before, but is now fully homegrown (as per Eliocroca CB's manager LOPO_s' original definition of homegrown - or we could add a link to a MrJs' article too) but has received a current salary benefit by buying own draftees back. In this case, the amount of benefit in $ would be mentioned in parenthesis after a + sign.
For instance, you've initially sold 3 players with total wages of $15000, and now buy them back and their total salary is $215000, so by your team in that table there would read "+ ($200000).
I think this would be very welcoming addition, so that everyone can see with a one glance which kind of former strategy each one of us have chosen, and most importantly, whether or not we have received a salary (read: skill) benefits by purchasing back our own draftees. :)