Marketplace

Navigate online marketplaces as buyer, seller, or builder with platform comparison, listing optimization, and scam detection.

Architecture

Role-based guidance for marketplace participation. Load relevant file based on user's role.

text

marketplace/
├── buyer.md      # Price comparison, scam detection, negotiation
├── seller.md     # Listing creation, pricing, platform rules
├── builder.md    # Marketplace creation, economics, liquidity
├── arbitrage.md  # Price gaps, ROI calculations, ToS risks
└── compliance.md # Tax obligations, legal pitfalls, bans

Quick Reference

Role	File	When to Load
Buying items	buyer.md	Comparing prices, spotting scams, negotiating
Selling items	seller.md	Creating listings, pricing, handling buyers
Building marketplace	builder.md	Designing platform, economics, payments
Arbitrage/Reselling	arbitrage.md	Finding price gaps, calculating true ROI
Legal/Tax questions	compliance.md	Tax nexus, ToS violations, suspensions

Core Rules

1. Platform-Specific, Never Generic

• Each platform has unique fees, rules, and dynamics
• eBay auction ≠ Amazon Buy Box ≠ FB Marketplace negotiation
• ALWAYS specify which platform advice applies to

2. Total Cost, Not Sticker Price

• Include: platform fees, shipping, taxes, return costs
• Amazon referral fee varies 8-45% by category
• eBay 13%+ Poshmark 20%+ Mercari varies

3. Scam Pattern Recognition

• Stock photos on local marketplaces = red flag
• "Ship to my address, I'll pay extra" = triangulation fraud
• Payment outside platform = no protection
• New account + high-value item + urgency = likely scam

4. Pricing Research = SOLD, Not Listed

• Listed prices mean nothing—items don't sell at listed price
• Always research completed/sold listings
• Factor in condition: "Good" vs "Very Good" = 30% price difference

5. Suspension Risks Are Real

• Amazon ODR >1% = account death
• Review manipulation = permanent ban
• IP complaints from brands = immediate suspension
• Multiple accounts = instant termination

6. Fee Complexity

Never estimate fees—calculate exactly:

• Amazon: referral + FBA + storage + return processing + advertising
• eBay: final value (category-specific) + promoted listings + payment
• Factor returns into margin (15-30% in some categories)

7. Real-Time Data Required

• Never quote prices from memory/training data
• Inventory and pricing change hourly
• Competitor stock levels affect optimal pricing
• Always verify current marketplace state before advising