I already told him it would be ok. He sees me at least once a week so don't want to cancel as don't want to lose his business. I do let him get away with more than others but that's probably my personal feelings getting in the way.
Will let you know how it pans out. I seriously don't think he would jeopardise not seeing me again.

It's not really business if you're giving it away for free, and if you really believe he's skint he won't be able to afford to go see another hooker before pay day..

Nope, never. I had a reg show up at my hotel for our booking then called me from next to the lobby cash machine to say he had accidentally left his wallet at work. Even though I knew he would pay me next time, I didn't want to take that risk as I would absolutely resent them.

Another time, my client got all the way up to my apartment to realise he left his wallet in the car. He looked at me expectantly as if to say "can it wait til after?". No chance.

Give a client any glimmer of special treatment and it then becomes the norm. Give them an extra 10 mins, before you know it, it will be an expected thing. 

I wouldn't do it. Come on thats not how the game is played. Maybe go out with him for a drink and comfort him, but let him know you have principles.