The "paper-work" Anatomy of a Wholesale

This is what confuses young investor the most. So any seasoned wholesalers’ your knowledge would be greatly appreciated.Saying price and contingincies with both seller and buyer are finalized. This is what I understand:

When dealing with assignment of contract:

Me and seller: We both sign Purchase and sales contract

Questions:

1)Do we need to have witnesses or sign with a person who can notarize? It seems very unoffical to just draw up a contract and sign…
2)Is it more common to do a letter of intent first the day you agree to terms and then follow it up quickly with the s&p on another day(incase in question 1 you have toget it notarized and make an appt)?
3)Even with “and or assigns” can i still purchase the property myself with hard money lender mortgage company if I change my mind about assigning the contract and want to rehab myself, or hold for investment?
4) To protect myself incase the seller tries to sell after we have signed the s&p…do you have them sign an affadavit/memorandum

Me and Buyer (still when assigning)
As I believe: After we agree to price sold, fees, verify funds, and I collect deposit: All we do is draw up the assignment agreement and sign

Questions:
1)Again do we need witnesses and it to be notarized
2)What would be used as the reciept for the nonrefundable assignment fee
deposit
3)After I fax this contract to closing agent am I done?What happens next?What if buyer backs out

Now If I choose to DOUBLE CLOSE

Me and Seller(before going to closing agent): Sign Purchase and Sales contract, and then would I have them sign affadavit/memorandum to gain rghts incase they try to go around my back with another buyer?(same as my assigning question)
Questions:
1)Same as before: do I need to have witnesses and or get s&p notorized…same thing with affadavit/memorandum
2)I still fax s&p over to closing agent to start title work
3)

Me and Buyer(pre closing agent)

We just sign the s&p and I fax that over to the closing agent

Do I need anything like an affadavit or memorandum? Again does this need to be notorized?How long do you usually wait to close when you get the buyer to sign the s&p?And what do you use the s&p contract as a reciept for earnest money/deposit

Now at the closing

We close simultanously…buyer brings funds and buys property from me(s&p contract)…Then I Buy property from original seller(s&p contract)

Questions:

1)Do I bring original s&p contract with me to show reciept for deposit of buyer
2)Do you always sign s&p contract with buyer first and then sign with original seller last