Is it acceptable to hire a provider as a trainer first?

[Ben]

...without him knowing, for a few weeks, to build up some fantasy tension, then hire him for the job later?

[+ FrankR]

1 hour ago, Ben said:

...without him knowing, for a few weeks, to build up some fantasy tension, then hire him for the job later?

Sure, as long as you are respectful of his career as a trainer.   And are prepared for the fantasy tension to be one-way and go unreciprocated (you may not be his type after all).

[MscleLovr]

2 hours ago, Ben said:

for a few weeks, to build up some fantasy tension, then hire him for the job later?

I wonder if the OP has discovered that the trainer actually offers extra personal services? 
If that is the case, I feel it’s better to say (earlier rather than later) that you find him attractive and want to hire him for more than training. 
Otherwise, it seems creepy.

If it’s just a fantasy in the OP’s mind, then @FrankR has given excellent advice

[j r]

Maybe you could consider letting him know up front that you are interested in his extra personal services but that you also want to work with him as a trainer and that you have a fantasy where he teases you for several weeks or months before you take it to the next level? Why not be upfront and let him in on it so he can help make your fantasy even better by purposely teasing you in the training sessions?

[+ RyanDean]

Having dabbled (mostly unsuccessfully) with this scenario, I would strongly recommend @j r's strategy.
Let him participate in shaping how the two aspects of the experience play through and you might have better results.

[+ KensingtonHomo]

49 minutes ago, j r said:

Maybe you could consider letting him know up front that you are interested in his extra personal services but that you also want to work with him as a trainer and that you have a fantasy where he teases you for several weeks or months before you take it to the next level? Why not be upfront and let him in on it so he can help make your fantasy even better by purposely teasing you in the training sessions?

THIS! I find so many men (maybe women and NBs too) work up fantasies in their head and seem to think that sharing them with their intended paramour will ruin it. If this trainer is also an escort (and we're assuming he is), then you can have an honest discussion about what you want. Perhaps you can even sketch out a scene where, during the fourth or fifth session, he takes it sexual. And, again, depending on where you're working out - not a public gym, obviously - this pre-discussion could set up a very hot scene. Doing it any other way risks surprising and upsetting the provider, and you being rejected - not because he wouldn't have you as an escort client - but because you weren't upfront with him. 

[Peter Eater]

3 hours ago, MscleLovr said:

it seems creepy

Yes, a stalker vibe.