So I have this idea. I create an open-source toolkit for sentiment analysis. It will be data-driven, not rule-based. So it can fit most use cases well. It'll be a full package with GUI, for labeling, training, and an API server to self-host the model.
I keep a private repo of data to generate a good-enough model for a niche: customer service chatbots. A part of which is curated (scraped), and a part is labeled by myself. I sell a subscription to the model, during which period, I try to gather and label more data to improve the model. I can design the system to support partial training. That is, the customer can improve based on my model, using just hundreds of lines of their own data.
I figured if I priced it the right way (10-20% of hiring someone to create one), I can sell it to dev shops and agencies. I can go to Linkedin or Upwork to approach my customers.
Does this sound like a viable idea for a one-man shop?
To proof me wrong, just try to sell the idea as a not yet existent or as a fake product. Build a landing page where people can subscribe to get further information, lead a few prospects to this page and count the subscriptions.
You seem to have missed one trick though: offering a 10-20% discount in return for adding their (labelled) data to the common training corpus.
Business is not based on making good stuff.
Business is based on selling stuff.
Or to put it another way, technical development is the inverse of a con.
Good luck.