Micro-niches are very profitable in terms of Adsense revenue. You target a specific amount of keywords with monthly searches not more than 6000-8000. Cpc is always 2$+. You can add a pillar content of...

Multivendor Marketplace is trending nowadays. You can just create a marketplace ecommerce website if you don't have inventory or goods to sell. Just take % commissions or Fixed price per product sale....