Well, you can really structure the deals however you want.
Financially, if you are still going for the banks, they will want a lot of the same information as you had for previous residential deals. Good credit, previous income statements and tax information, the whole nine yards.
Also, I've made it a habit of having a five-year pro forma with me, along with my business plan and a property overview. These are things I prepare for investors, mostly, but they are also nice for the bank. Things like capitalization rates become more important for an apartment complex, because cashflow becomes more important with it.
Another good figure is the debt service coverage ratio, which basically shows how many times over you can pay your yearly mortgage. It varies between banks and the amount you are getting, your down payment, and everything else, but generally they'll want a ratio of 1.2 or higher.
As for the seller financing, that's where deals can get kind of creative. I've personally never used any sort of seller financing or land contract for a down payment, simply because I haven't really had sellers that like that idea. The idea of them getting the sale money, paying off the rest of their loans, and then loaning you the down payment isn't always what they want, since they could otherwise take that money and 1031 it into another property or invest it elsewhere.
When you get into even bigger deals, where prices run well over seven figures, there's always things like mezzanine financing and all this other wacky stuff that works, but that's a horse of a different color. If you can't finance the down payment through a land contract, and hard money lending isn't available, you usually have to raise it yourself.
Of course, this is just my experience. Take it with a grain of salt. You might find a seller who would be willing to finance your down payment, and that's between you and the seller. I've just never been able to find someone like that.