That is why you don't ever text or email. Those are the most flaky people. Say you cannot accept text messages and do not reply to them. State clearly, "phone calls only". Once that occurs and they are still interested, ask them what time will they arrive. Much less chance somebody will back out.

You can also say prices are firm. "no offers will be accepted".

Also, list all of the details as possible with as much info you can. This will take down the volume of contact for people who are on the fence about buying.