so how do you get funding for the down payment?

[Benjamin Cowles]

or just any secondary loan. How does the lender benefit from a 2nd mortgage? A higher interest rate? Is that it? From what I understand with a subordinate mortgage there is no room for any collateral for any loan below the first. So.. a higher rate and credit requirement is what I should expect? 

A lender is offering 70% LTV at 8% interest rate. So it would be nice to cover some of that 30% down payment.

Or should I do a buy and hold deal 50/50 with a partner to split that down  payment and I was thinking taking advantage of the opportunity to get experience partnering with someone seems like a good person to work with?

what are common methods/strategies to cover the down payment? So far I've quickly got in the habit of bringing up seller financing and in the short of time I've been doing this and the shamefully little work I've done I'm surprised to report I've talked to a few at least open to the idea. But however I work it I'm wondering what my options could be with financing the down payment. 

[Ned Carey]

Generally you do not borrow the down payment.  Most time the lender in 1st position will not allow it. They want YOU to have money in the deal so you have a strong incentive to make the deal work.

Save up and invest your own money is by far the most common. While No money down is possible and @Brandon Turner wrote a book on the subject it is not the norm. Even when you can structure a no money down it is still wise to have cash reserves for inevitable problems.