What does a lean AI market research stack look like for a bootstrapped founder?

You can cover 90 percent of early-stage research needs for under 50 dollars a month: one deep-research chatbot (ChatGPT, Claude, Gemini, or Perplexity) for desk research, NotebookLM as a free grounded workspace for synthesizing everything you collect, a community or audience signal tool (Reddit search, SparkToro, or Google Trends), and a simple survey or interview tool when you need primary data. Buy specialist platforms only when a specific decision justifies it. The stack matters less than the loop: AI for breadth, real customers for truth.

A quick orientation. The real value is below: resources worth your time, from people who've actually done it.