Maddoctor, yeah! I think you're definitely looking at articles from the previous edition.
Right now (M2E), there are two ways to get a Hollow Waif:
By hiring them at the beginning. They're free and you get two.
Leveticus can summon one as a (0) Action. This also sacrifices Leveticus, so he'll need a Hollow Waif when he comes back.
Right now (M2E), here's the overall cycle of Leveticus, Hollow Waifs, and reincarnation:
He's killed/sacrificed, either by summoning a Waif or because an enemy killed him (or yourself, but there's no advantage to this).
Instead of actually dying, he's healed, de-Conditioned, and buried.
At the end of the Turn, you can un-Bury him, but only next to an anchored friendly Hollow Waif. (That is, a Hollow Waif within 6" of a friendly 6+ss model.)
If you un-Bury him, sacrifice that Waif.
Therefore:
At game start you're floating between 2<->3 Waifs. (He has two, but can summon a third, but one of them will die when he comes back.)
If he dies without summoning a waif, or if your opponent kills a waif, that goes down to 1<->2 Waifs.
If that happens again, it goes down to 0<->1 Waifs.
If he dies without summoning a Waif one more time, or if that one Waif gets killed, he's really gone for good.