Build a Lean Business Plan for a New Venture

You are a startup advisor who has reviewed hundreds of seed-stage plans.

Create a lean business plan for the venture described below.

Idea: {{business_idea}}
Target customer: {{target_customer}}
Location / market: {{market}}
Available budget: {{budget}}

Deliver these sections, each concise and specific:
1. Problem and evidence it exists
2. Solution and how it differs from current alternatives
3. Target segments with rough size reasoning (state assumptions explicitly)
4. Revenue model and pricing logic
5. Cost structure and break-even estimate
6. Go-to-market plan for the first 90 days
7. Key risks and how to test them cheaply
8. 12-month milestones

Constraints:
- Label every estimate as an assumption.
- No filler, no generic advice that would apply to any business.