Two-Sided Marketplace

# Requirements Specification: Two-Sided Marketplace

## Overview
A peer-to-peer marketplace connecting sellers (individuals or small businesses) with buyers looking for unique or secondhand items.

## User Personas

### Seller
- Lists items for sale with photos and descriptions
- Sets prices and shipping options
- Manages orders and shipping
- Receives payments after successful delivery

### Buyer
- Browses and searches for items
- Messages sellers with questions
- Purchases items with secure checkout
- Leaves reviews after receiving items

## Features

### F1: Seller Onboarding
**Priority:** P0 - Critical

#### User Stories
- As a seller, I want to create a seller profile with bio and photo
- As a seller, I want to connect my bank account for payouts
- As a seller, I want to set my shipping preferences

#### Acceptance Criteria
- [ ] Stripe Connect onboarding flow
- [ ] Identity verification for sellers over $600/year
- [ ] Seller profile shows rating and number of sales
- [ ] Shipping options: free, flat rate, calculated

### F2: Product Listings
**Priority:** P0 - Critical

#### User Stories
- As a seller, I want to create listings with multiple photos
- As a seller, I want to set price, condition, and category
- As a buyer, I want to search and filter listings

#### Acceptance Criteria
- [ ] Up to 10 photos per listing
- [ ] Categories with subcategories
- [ ] Conditions: New, Like New, Good, Fair
- [ ] Full-text search with Algolia
- [ ] Filters: price, condition, location, shipping

### F3: Messaging
**Priority:** P1 - High

#### User Stories
- As a buyer, I want to message sellers about listings
- As a seller, I want to receive notifications for new messages
- As a user, I want conversation history preserved

#### Acceptance Criteria
- [ ] Real-time messaging with Socket.io
- [ ] Push notifications for new messages
- [ ] Messages linked to specific listings
- [ ] Report/block functionality

### F4: Checkout & Payments
**Priority:** P0 - Critical

#### User Stories
- As a buyer, I want to purchase with credit card
- As a buyer, I want shipping tracking
- As a seller, I want automatic payouts after delivery

#### Acceptance Criteria
- [ ] Stripe checkout with saved cards
- [ ] Platform takes 10% commission
- [ ] Funds held until delivery confirmed
- [ ] Automatic payout 3 days after delivery
- [ ] Dispute resolution process

### F5: Reviews & Ratings
**Priority:** P1 - High

#### Acceptance Criteria
- [ ] Buyers can leave 1-5 star reviews
- [ ] Reviews visible on seller profile
- [ ] Sellers can respond to reviews
- [ ] Review required within 14 days of delivery