Both of these can be negotiated freely, so both the worker and the seller are willing to do the trade.
And you still don't understand that all Capitalists do is take portions of productivity of every worker, he doesn't help them at all, he exploits their bad position (needing $ to live)
This is NOT all they do. One person can build a small bridge. A big bridge requires many people. A huge bridge even more people. Organization of those people is hard.
