​A couple newb questions about simple and compound interest and mortgages.

[Benjamin Cowles]

When figuring out the 'seller finance' terms with your seller or buyer how does simple and compound interest figure into it? 

I read that mortgages use simple and I also read they use compound interest. Who's the expert in this part, or who plays an expert how do they put it out 'on the table' to discuss and review with the prospect?

And what are the details of this aspect to consider? Speaking of which, do you create a mortgage with a note or can't a guy off the street make one, or what functions for the purpose of a mortgage for an investor?

Thanks!