I don’t have any direct experience with legal prostitution, being female, but a good friend of mine has a great story about prostitution in Amsterdam.
He was vacationing over the puddle, visiting a Dutch friend. He wanted to check out the red light district one night, and his friend was more than happy to take him down there. They had a few drinks, and proceeded to walk around the area. One section has buildings with open windows through which you can see the girls. They perused this area until my friend - I’ll call him D - found a girl he liked. He went in, and quickly negotiated a price. A short time later he found himself in a small room with the prostitute.
The prostitute started in with him, playing with his crotch and talking. She started to remove her clothes, and after a bit, removed her underwear. D was a bit surprised to see that she had another pair of underwear on underneath the first pair, but by then was into the whole experience enough not to think too much of it. Then the prostitute got down on all fours, and looked up at him, inviting him to sex doggy-style. He was also a bit surprised at this - it usually cost more that way. No worries, though, if she wanted it doggy style he was more than willing to help. He reached down to remove the last piece of clothing barring his way to actual penetration - the second set of underwear. He took 'em off. The prostitute’s penis flopped out.
D. very quickly got up, got dressed, and went outside to meet his friend who’d been waiting for him. His friend was laughing his ass off - it seems he’d known the whole time that the prostitute was male. Amazingly enough, D. still talks to this guy.
Be careful when choosing a prostitute in Amsterdam.