Sure we'll pay you, but the only place you can shop is the company store.
We already see something similar at law firms - partnership in a firm means literally buying into it, and one of the perks you receive at many law firms is the ability to take out a loan at favorable rates, particularly to help with said buying in.
Some form of coops Mondragon for example do but that is a very different type of employment.
In general, a partnership is a collection of equity owners ("the partners"). To become a partner you have to buy equity, usually sold by a retiring partner.
Sometimes "new partners" are created by diluting the stock; this is generally avoided unless the person is expected to grow the business by at least that much.