First time seller with. Seller Central, money question…

I understand that while it is free to sell on Seller Central that one should have a good amount of money in the bank because Amazon pays only every two weeks. So as a POD seller, I was told that the POD print providers will not wait to be paid. So how much money by your experience, should I have in the bank before uploading my products to seller central? I mean, what if one of my products go viral?