I am doing a Saggi quest and one of the items is 30mil and I only have 13mil... I heard that some people are borrowing money and paying them back when they get a large payout so I am wondering how this works :P

there's no official mechanism for doing anything like this, so there will be no enforcement of any such deal. Either you know someone and can make a deal with them, or you have collateral and go to the wanted boards and make a deal.

Saggitarius' quests as they are now constituted tend to be pretty good about returning a value close to that of the items that he asks for nowadays, but he doesn't always do this, so it is a risk on your part and another on whomever loans it to you. Also, he has been changed once already since the new version has been released, so there might be another change implemented in between you getting your capital and making your deal.

Thanks for that, I think I'll leave it then, if there is no guaranteed profit I will not risk someone sP. I will save so I can use my own :)