I usually see the same guys over and over, so I use the visible envelope method. When I’ve had providers ask upfront, it’s been fine, although on a personal level, I found it off-putting when one provider I’d seen before counted it in front of me.
My general view when seeing new is to follow the provider’s lead. By the time I see someone, I’ve tried to find out info about them. I don’t see guys who have multiple allegations on RM or here of having done runners. So at that point, I’m not concerned about getting ripped off.
Waiting until the end can be awkward too. The first time I met one of my regulars, he initiated everything pretty quickly, we moved locations, and I left the donation in my jacket in the living room. Afterwards, he followed me back to my jacket, which I didn’t think about until he visibly relaxed when I pulled out an envelope.