1) I have indivualized this. Before even writing the invoice I will have a long and sup-friendly chat over coffee with the accounting person or whoever takes care of thee billing in that shop. I let them explain in detail their process. I always learn something interesting about how the real world works. I listen. I listen to their woes, I sincerely try to understand them, their problems act everything. I establish rapport with that person. Finally I ask: "OK, now, how are we going to go about this?" At this point I normally have enough of an idea about their process to understand what kind of dates and other terms would make it work. I always highlight mutual respect.

2) First of all, normally I do not start to work before I received the money upfront. Well, the money for the current milestone of the project. This is the best way to make sure you don't waste time with people who don't want to pay.

Second, I am not only willing to give a discount, I always use this to sell the offer I want them to buy the most. But I never do an unreal number like "2%". What is that? Have you ever seen a 2% running in the wild? I don't know any bank or corporate office that work so fast that they give you the money on the sam day. Unless you are talking about "small" clients who work via pay-pal and the like?

3) I don't understand the question?