I assume you are referring to a lady you've never visited before? The ladies I have seen numerous times and know me sometimes can't respond immediately and do respond sooner or later. This is fine with me, and the ladies that I know are aware they can text me anytime, but I know everyones situations are different.
As far as first contact, as it was brought up earlier, it is good practice for a lady not to contact if after an hour or so as she doesn't know the clients situation. I too subscribe to the 2 strike rule. As for the time frame between texts, it depends on your situation. Often times when I know I have a day off the next day I may contact a lady mid morning. If I don't get a reply by early evening, I may text again in hopes to book the next day. I do this because I understand the ladies have lives and aren't able to respond immediately. When they are able to respond, they may be inundated with a days worth of texts to sift through. My evening text might, and has, put me at the top of the pile. Of course cordial and respectful texts are my rule. Often times I receive a response the next morning so my day off wasn't a total loss.
I do stick to my 2 strike rule. If I receive no response after 2 texts or emails, I move on. She may have reservations about me for whatever her reason and this is her right. She may be unorganized and unprofessional, probably someone I don't want to spend time with anyway. Whatever her reason, I believe no response is a response and leave it at that.