The problem is that this makes it friction-free for the student ... and the actual trade? Your wage. It takes away risk, which everybody likes, until the costs of that start accumulating. It's an excellent way to give the student a very strong reason to avoid applying anywhere else (and make applying elsewhere far less successful), and so effectively to pay them (much) less.

Get a PhD with years of experience, who knows your company, for the price of a secretary.