Honestly, I think asking if XYZ niche is big enough is a complete waste of time. I think a lot of investors are missing a lot of round-the-base home runs because they want to chase grand slams. If you fund an idea that’s profitable at as little as$300K/yr, but you have an ambitious, creative founder that now owns a business that could fund unlimited projects until it produces the one that hits product/market fit on a larger market.