I don't mind short-notice clients, either. I think it's common for men to have a meeting cancelled and have an immediate window of time open. So, I'm not put off that they ask. But I think it's funny when they seem to expect me to be within five minutes of them, ready for them.
If someone were literally five minutes away and I were ready, I'd still probably want ten minutes to make good and sure everything were in order. But most of them call from the main train station. Those same ones don't know the city centre that well and want to walk to me. I feel like a heel suggesting they take a taxi because I know I'm a bit profligate in that regard and take taxis all the time. But walking to mine will take about fifteen or twenty minutes and the directions would be hard to give over the phone. Either they need to have good access to Google maps or they need a taxi to get to me easily.
However, I've certainly had some lovely gents walk to me, updating me on the fact that they're lost, and being generally cheerful about it.