How do I double close in California? + More Questions

[Danny Leyva]

It's my first ever real estate deal and i have enough spread on a property that i dont want the motivated seller or end buyer to know what i will be making off the deal. 

I saw one video saying that i should make a purchase agreement (or CA RPA in California) between me and the seller, and then to make a second purchase agreement between me and the end buyer. My question is, is this legal in California? 

Do i sign the agreement with the end buyer before the property is mine so the buyer has enough time to show up to the title company with the purchase price money, or do i sign it at the title company first and then wait for them to get financing?

Will this work if the end buyer gets a mortgage? I know banks will fight against an assignment if they see it, so does this agreement  with the buyer protect me from possible issues with their bank?

In my contract with the seller, can i agree to pay cash with 0 earnest money, pay him from the end buyer's purchase price money that the escrow company is holding, and pay all escrow/title fees with the same money? 

Is it better to do a CA RPA with the end buyer or a CAR addendum and how would i get paid with the addendum?

I know this may be a lot to answer, but i am fully committed to giving all my effort to real estate and i greatly appreciate the time you take to write a response. Thanks