You can definitely be profitable renting at Silver and Gold, and I do myself at Diamond (I have literally 0 cards playable in the league I play in, all rentals). You have to be patient and accept the reality of slowly profiting and grinding. But it is rewarding, and it is possible man.

There's a a lot more involved in this, and I'm actually writing a deep dive on those things, I'd love to hear your opinion once I'm done.