Question about the logistics of an owner financed deal

[Dave Klein]

Up until now I've always bought relatively small(ish) deals and always put 20% down on my multifamily properties. I'm starting to look larger in the range of $500-1.5M and if I want to continually buy these saving the 20% down each time is going to limit me.
I've talked to my bank and they are fine giving me the 80% on a good deal up to 1.5M but won't finance the entire amount. If I can get an owner to carry back a 20% or 10% second mortgage how do the logistics of that work? I kind of assumed that the title company could set up the 2nd mortgage with the monthly payments and calculate the principal/interest for a fee of course but when I called my regular title company they made it seem like I was talking a foreign language.

Who handles the administration of your owner financed deals??