Since you have picked your escrow/title company, you should contact them before you go any further, and find out what the proper procedure is. They know the law, and they will want to follow a specific process.
Has the buyer agreed to this company?
Are you confident that you can write a legal contract?
All funds should go into escrow - not to the seller. That's the whole purpose of using escrow - it protects the buyer. In fact, the law I mentioned above,
requires you to use escrow. If the money is sent to you - you aren't using escrow.
An escrow is: an arrangement where an independent trusted third-party receives and disburses money and/or documents for two or more transacting parties, with the timing of such disbursement by the third-party dependent on the performance by the parties of agreed-upon contractual provisions
As a buyer, I would want to send a small good faith deposit, and then the balance after I received the
estoppel letter.
*If you have more questions about selling this property, please post them in this thread, instead of starting a new one, for continuity.