In the modern Russian the word ''кормилец'' is used only as a legal term for a working person who earns money to support his/her dependents, a breadwinner. When this person dies, the dependents may be entitled to certain allowance. ''Поилец'' is a theoretically existing but never used word, built by analogy with the first one (i.e. a person who not only brings something to eat, but aslo brings something to drink) I would recomment to you not to use first one outside of a legal context and not to use the second one at all.

Пои́лец и корми́лец — человек, который поит и кормит, содержит семью. а так же: Корми́лица — это женщина, нанимаемая для кормления грудью чужого ребёнка (и, нередко, для ухода за ним).

Это очень широкое понятие, вплоть до тго что так можно назвать и орудие труда для зарабатывания денег. Например для таксиста это его машина - "кормилица и поилица" Причём "поилица" имеет ещё одно переносное значение.. :)

For my experience i know that the term "кормилец" is used not only for men, but for animals and inanimate objects. For example, my grandmother called her cow with this word, because it was really hard to live in the village without a cow. I also heard that a man called his truck buy this word, because it was the only way to get money for him buy transporting wood. And yes, we don't use the word "поилица"

Ну не все, это вы преувеличиваете.:)