I still confused... which software I should buy. How much we have to pay for vBulletin? Is the license transferable? in case I plan to sell it in future?
oh my god,I need to suggest that the best forum software is Discuz x2.5 or phpwind,and they are free to use and open source,spend money before you can make money from it is not my appetite,I would suggest you to have a try on the aforementioned forum software it only has Chinese version though,but you can translate it to your language,do not doult me ,it is the world most powerful software that I ever use,the functions are beyond your imagination,user credit?user center?That's built-in functions you can attain that even without installing add-ons,have a try,here is my article for that, http://hub.chnmoneys.com/index.php?threads/leading-open-source-forum-software-phpwind-and-discuz.1/
Discuz is not bad, but I will suggest Xenforo more than. One of thing you should know: Xenforo need to have VPS more than standart hosting, cause it has some special requires for running well.