I better win a "best answer" for this.
First off, I am not a lawyer, so you would need to consult a lawyer to interpret the contract. I am a broker for my company. This is what we allow.
You CAN write a "100% cash offer" and then decide to get financing.
1) You have to show that you COULD in theory buy it with all cash. Proof of cash in a checking account or liquid stocks should suffice.
2) The contract has NO finance contingencies (no appraisal contingencies)
3) Section 13 of the VA contract allows you to change the type of financing at any time, as long as you don't delay the closing or cost the seller even a dime.
So if you initially said all CASH, but some lender offers you a great deal, you can get the loan. At closing the seller won't care if you bring Cash Cash or Bank Cash. But if you mess up, they will hold you in DEFAULT.
What you do NOT want to do is pretend that you can buy it with cash and then get a loan.
Best of luck
Frank- Broker FranklyRealty.com