For what it's worth, I don't think that if you like someone as their client you would move naturally to a relationship. The only time I've come close was fucking someone (extended trip abroad) who was a totally fucking useless shag. I pretty well told her so by ignoring her every time I subsequently popped into the RLD where she worked. Eventually she hassled me about it and and I just told her, look, you weren't very good! She was a bit fucked off but still kept insisting she wanted to see me. I told her no way.
This went on for three weeks, including her sister intervening on her behalf. I didn't want to waste time even seeing her for a coffee. I think eventually I agreed to meet her for a coffee, I don't know why. She was very sincere, said she wasn't interested in me as a customer though didn't go as far as saying she thought I was a crap shag too, which is what I'd told her she was. She was pretty sweet and I was bored anyway and thought oh what the fuck and let her pop round to the apartment. She worked hard to turn on the charm. Told her no but said it was nice meeting her (she'd been pleasant, after all). Saw her again for a coffee. She'd bought me a small present. I was warming to her a bit and hadn't had a shag that day so let her stay. This time she was dynamite in bed. I asked her why the change and she went a bit mental and said the other time was work and what did I expect going to 'a place like that' blahblah. Ok. I walked her to the train station and thought, she's not that well off and she did buy me a present and give me a decent shag. So the generous part of me tried to slip a bit of cash into the top of her handbag.
Of course, the wee fucker went fucking ballistic, threw the money at me, started to claw my eyes out and accused me of treating her like a whore and blahblahblah. Ok, I relented. Saw her for the remaining fortnight before I had to leave. Hope that answers the question.