56harrisond

I avoid establishing a hard line rule of # of hours to be considered a reasonable period of time. It varies, with something reasonable falling between 2-hrs and 24 hrs. Your provider could be on a flight with no reception when you text. Or sleeping during the night, or at their day job if they have one. They could be in a remote place with little to no reception for a time. Who knows. Most providers in most normal situations will get back to you within a few hours or less if they are going to respond at all.
If a client wants to meet a particular provider, I highly recommend booking ahead a few days, or at least 24 hrs in advance. That puts you in a priority position so others have to book around your appointment or otherwise be out of luck because you planned ahead.
If the client has a very limited window of availability, such as only a few hours after meetings while on a business trip in the provider’s city, then I recommend booking a week or more ahead, at least a few days. It’s unlikely the provider will be available during that particular limited window on short notice that same day/night.
If your first choice provider does not respond within a reasonable time, you can safely assume it’s unlikely to work and move on to contacting alternate ones. If your schedule is more flexible on day/time and you’re both in the same city for a period of time, it may be worth trying again. If they don’t respond at all, bad sign, move on.
If you’re wanting company from any number of providers and you don’t particularly care which one exactly you are going to see, by all means, feel free to contact multiple for that same day/night, same hour / “right now” and see who responds. Some of them may be available on short notice and some won’t.
Keep in mind when texting a provider same day or short notice, you’re asking in so many words if the provider is available to respond to your text at that very moment (or within that reasonable period of time after your text) AND available to fulfill your appointment time request which may only be a couple hours after that. In total, you might be asking for the provider to be “available”in some sense for half a day, from start to finish from the time you first text to the time to get ready, time for either of you to travel, to the time the appointment actually ends. Plus travel time after the appointment ends, if applicable. That’s a lot to ask of a provider on short notice. Sometimes you luck out and it works out just that easy. Oftentimes not. Which is why I recommend booking ahead, at least 24 hrs. More is better whenever possible.
Planning ahead buys you a much better chance of getting exactly what you want with who you want, when you want. If your provider doesn’t respond within a day, you have the extra time to request alternates.