I'm not easy with the concept of getting an /unlimited amount of merits to send

You forget to click button "Send" Grin

Merit source don't have unlimited amount of sMerit either

Well, technically it's kinda sorta unlimited. As long as you're a merit source you can't run out of sMerits, not permanently anyway.

Does that mean people have unlimited money if they stable jobs with stable income?

You also haven't earned much merit since the merit system was born. I do not see much opportunity for you to be accepted Roll Eyes

I've seen few merit source with low amount of earned merit, it shouldn't be big problem.