Seller Financing - Down payment, interest, and managing note

[Jonathan Ruiz]

Looking to purchase a single family home in my neighborhood. Owner has pasted, heirs inherited the property. Property is owned out right. 

What's the best to structure a seller finance deal? 

What kind of interest rate should I propose? 

Is there a company that can manage the payments for us? Clearly defining the remain principle balance as get out in time? Is there a company that purchases owner financed notes? 

Thanks in advance.