I wish you success in growing your YouTube channel. I heard you need to keep posting even when you get no views for months and then suddenly YT algo will start promoting you. I never managed to push through this initial stage, so it will be interesting to see someone succeed. Maybe also try...
In general, billboards are best for restaurants and shops. Ask yourself if someone needs more than a few seconds to understand your business. If so, it's probably not worth it. Though, you can also try reselling it for a profit.