Assignable Contracts/ Double Closings

[Janet Balian]

Hi everyone, I hope you're all having a good day. I had a question about vaild contracts. Do I need to get an assignment contract from a title company, a lawyer? Is it a contract that I can print online, or do I need to create it each time specifically for the deal and get it approved by a lawyer and title company? Is a double close contract along the same lines but separate for each party? 
May I have examples of empty templates or a checklist of what needs to be included in an assignable contract? Thank you!