Wind and solar projects, even residential solar, is very easy to finance. Even batteries can be financed. Upfront cost is not an issue. Sunrun (the biggest residential solar installer) has a deal right now where new customers will only $1 / mo for their first 6 months. They package those systems with batteries, now, too.
Battery costs still have room to go down (and they will), but they've already fallen substantially.
More importantly, other energy storage technologies are emerging. It's not just batteries. This is important, of course. There is a lot of pumped hydro, already, that will continue to be used, but there aren't many opportunities to develop new projects like that.
That said, the intermittency of wind and solar can be managed to a large extent by curtailment, even at high penetration levels of 50% and above, even if without much storage because gas generation is very flexible and is what keeps the grid balanced.