How exactly does one set up financing with private investors?

[Kristin Towle]

Hi! My sisters and I are forming a partnership and buying rental properties. We want to find some private investors to finance the down payments, in the form of loaning money to us at an annual 10% or so rate. 

How do we draw up a contract? Do we use a notary?

And how do they give us the money? Do they write a check for us to put into our partnership's bank account?

How do we assure them that we will be accountable to them for their money and that we will accomplish our goals even though we are newbies?

If you can advise me on specific concrete steps to take and forms to use, I would greatly appreciate it! Thank you!