1. If there is prizemoney involved, would you pay a little fee for a season?
If the league is well organized for me doesnt need to be prizemoney to keep my interest and therefor no need for an entrance fee in my opinion. But if its top-notch organized, extremely user friendly, easy to get into, a lot of lfs buddies racing there, international and the fee not to high (~5€ for a season), then i wouldn't mind paying a fee.
2. What type of racing would you prefer? Sprints of 30 mins, longer races? open wheel or GT racing? Or both?
Personally i prefere a system of an about 10mins sprint race and a longer race (>60 Minutes ; < 80 Minutes) after with the top drivers reversed. 15 Minutes qualifying
There needs to be an international top organized non endurance GTR-League in my opinion.
3. What prizey would be needed to get you "hot" to definitely taking part in this?
Doesn't need any prizes just a top organization. I wouldn't get a prize anyway.
4. What else could you think of?
Some points i discovered for leagues in the past year which are important for me:
-easy registration/deregistration if you do have a real life its hard to make every race especially in longer seasons +4races
-if its a new car/combo every race i like 14 days racing rhythm due to the reason i mentioned the point above and because i want to start a race well prepared
-easy signup for the league, differs from registration. "signup" for the league, "register" for the race
-a good looking web page with all necessary information (up-to-date) but not to much information that you dont find the important things.
-fast event summary by the admins, including uploading replays, posting the results, stats and championship standings
-easy procedure to submit complaints
-experienced, independant admin and judging team