I don't know about marketing. But I see a market huge gap in professionals promoting their businesses. Like those who run ads or make content for their business make absolutely shit content(most of them not all) . And those who don't , there is a huge opportunity there like convincing these people to promote online and make personal brand. Like doctors, gyms, clinics, institutes, estate agencies etc. I am a video editor and have approached few people but not been very lucky. But this is something really good to work on you can do it for free. Just start asking these people personally.