Here's my comment about this: use escrow from this list:
https://bitcointalk.org/index.php?topic=855778.0If you plan to launch a service without using any escrow and if you expect people to send you their money first, then I already know what this is. I will wait for you to confirm your intentions... will your service use a trusted escrow or no escrow? The answer to that will determine if this is a scam in the making.
I know these are harsh words but it's always good to be blunt and direct. It helps keep things in perspective. I'm sure honest members of this community will agree.
I know you mentioned something about an escrow API but I also see you plan to introduce this later (i.e. "second step") which suggests you won't be using escrow in that crucial first stage of your plan. The critical loophole there is that you could simply stretch the "first stage" forever to maximize your window of opportunity to transact without escrow.
"Will see how it goes" implies uncertainty. All the more reason to use escrow on the day you launch this service and not 2 or 3 stages later.