It really depends upon how well you know your client and your client knows you. I can recollect I started working as a content writer and have worked for some big SEO agencies from bhw, as they were having large setup I haven't asked for upfront from them. But, for others I haven't ever worked without full upfront at least for first five seven deals. If I find them prompt with the payment, then I do work without upfront.
I guess, a couple of days back a guy searched my skype id from BHW and he reached me. He asked for the White hat SEO of the website and told me that I must not ask him for any upfront as if that website will rank for a keyword, he will sell it at $30k and then he is going to share 33% profit with me. He told for a long tail his website was ranking at 30 and he want it to be ranked it at #1 and believe me that keyword was damn easy to rank.
I told him that I am not interested in share you can pay me $275 as upfront or $100 as the cost of tools involved or tell me your bhw name.
He said- I won't pay you a dollar it's a JV. He also told me that I am not able to disclose my bhw user name. So, in case if you get any idiotic dumb like him please ask for the full upfront payment coz I am damn sure he was not having a single penny to pay me. I was asking payment just to get his paypal email and his details to ensure that he is reliable.
You can work for JR.VIPs without upfront or with 50% upfront in case of permanent work and for temporary you can ask for full upfront.