If someone was offering seller financing on say half the purchase price and your other funding source would only offer financing with a first mortgage would you attempt to get financing from the owner with a second mortgage? 

I would imagine in most if not all cases that would be out of the question but I don't really get the point of second mortgages from the viewpoint of a lender anyway with the outcome of the borrower defaulting and the position it puts the second mortgage holder in.  Then again I don't quite get the point of second mortgages from the viewpoint of the second mortgage holder as an investment. 

So am I wrong about this and second mortgages can be negotiated, and if so how so? How do you sell someone on a second mortgage?