Since Tartarus has been established many businessmen and even politicians wanted to send someone to train in the camp and become a professional bodyguard.
That's right, Tartarus wasn't established to train assassins but bodyguards. They have been training elite bodyguards from all over the world. These people were invited by politicians and other influential people to train then become their bodyguards. Of course, they are paying Lyca Shen and her company millions just to get an invite for the camp. In return, each of them would be trained as assassins and would be provided gears to guard those executives.