[quantumhobbit]

I wondered this too. How long could an investor wait before sending the "Yes" and have it still considered valid? Could the investor not reply for a few weeks or months and only send the "Yes" once the startup is growing and worth more than the initial deal's valuation?

I think there needs to be an explicit timer between step 3 and 4. Something on the scale of a few hours or at most a few days.

[dangrossman]

> Where no time is specified in the offer, the offeree has a reasonable period of time to accept the offer. After a reasonable period of time expires, the offeree's power to make a contract by accepting the offer "lapses". ... When a seller purports to accept an offer after it has lapsed by the expiration of time, the seller's acceptance is merely a counteroffer and does not create a contract unless that counteroffer is accepted by the buyer.

-- Anderson's Business Law, Formation of Contracts: Offer and Acceptance: Lapse of Time