Congrats on your steady growth on Twitter and YouTube - that's definitely a good sign that you're on the right track!

Sponsorship, brand integration, product placement, reviews, and endorsements are all good ways to make more income with your YouTube videos. Sponsorship would be like a regular, ongoing company that is mentioned at the start and/or end as helping make the video/show possible, brand integration would be making a video based around the company's product or service, product placement would be using the company's product briefly in a video, a review would be sharing your thoughts on the company's product or service, and an endorsement could just be saying at some point that you found a company with a product or service that you like and think your audience would as well.

Hope that helps and otherwise if you would like more information on any of those or ways to get companies involved, please feel free to request a call with me!