Help writing an offer!

Do I have to use a standard offer form to make an offer with seller financing on a 2nd position or can I just write it out myself? If so, how would i word something like this with conventional funding as a first position and seller as a 2nd position? I would appreciate some help. Thanks.

Are you a licensed to sell real estate in your state?

If your not licensed this is what I would do:

Just make an addendum to the contract for the 2nd position note. And in the financing section add a note to refer to addenda #1.