The phrase "tidak mungkin bisa [gan]" should be taken as a whole in order to put the sentence in its full context and grasp the underlying meaning or nuance. The colloquial 'gan' is taken from 'juragan' and is now commonly used as an informal term of address, especially among members of online Indonesian community 'Kaskus' . In this case, 'modal' refers to money, funds, forces, or resources. As regards the relaxed and informal atmosphere, the sentence 'Kalau tidak punya modal, tidak mungkin bisa gan' can be translated into English as follows: 'If you don't have enough money, you won't be succesful, mate/buddy.'

http://www.kaskus.co.id/profile/2153278

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Note added at 8 hrs (2013-08-08 02:04:38 GMT)
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typo: successful