Feature spec
Goal: Send a clear invoice after finishing a job.
- Add a client, line items, a due date, and payment instructions.
- Preview the total before exporting a PDF.
- Keep an editable draft if export fails.
App Overview
Back Market - Buy & Sell
Back Market is the best marketplace to snag premium quality refurbished tech like smartphones, laptops, game consoles, and tablets at up to 70% less than brand new
Free · In-app purchases
PRICE
Free
In-app purchases
BUSINESS MODEL
Freemium
No overall Grossing estimate available
RATING
★ 4.7
59,494 ratings · Top 15%
Evidence scope: No current overall US chart position is available. Category-chart positions shown in discovery are a separate scope. Revenue is a directional model estimate, not verified earnings.
Build your own version
Build Kit
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A product spec, screen plans, and build steps for your coding agent.
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What should your app do differently? Your note travels with the kit so your coding agent builds around your idea.
What's included17 files
A product spec, phased build plan, differentiation notes, and screen references.
- START_HERE
- AGENTS
- EVIDENCE
- SPEC
- BUILD_PLAN
- DIFFERENTIATION
- skills/
- screens/
Preview a sample Build Kit No email needed
Illustrative example: an invoice app for independent contractors. Your kit is tailored to the app you choose; this is not its generated content.
Screen plan
Invoice editor: Client at the top, editable line items in the middle, total and preview action at the bottom.
States: Empty draft, validation errors beside each field, exporting, and a retry action that preserves the draft.
Differentiate and validate
Hypothesis: Contractors need faster repeat invoices more than more templates.
First experiment: Test duplicating a previous job with five contractors. Watch where they hesitate before expanding the feature set.
The full kit adds a phased build plan, evidence notes, tool prompts, and implementation guidance. It is a plan for your coding agent, not a finished app.
Usage: Mechanics are fair game; never reuse the original name, branding, assets, or verbatim copy.
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Free quick prompt For a smaller starting point
Quick prompt
Good fit for mobile-first iOS and Android prototypes with managed app scaffolding.
// RORK SYSTEM PROMPT
Rork plan preview for Back Market - Buy & Sell: map the core Shopping workflow, choose the smallest differentiated feature set, define the data and monetization boundaries, then prototype the riskiest user journey first.
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Opportunities
AI-GENERATED OPPORTUNITY HYPOTHESES
These are generated suggestions, not verified review quotations. Check current App Store reviews and speak with users before treating a possible gap as a requirement.
Hypothesis 1
Implement advanced filtering by brand, condition, and features.
Assumption to check: Limited product filtering options
Validate with people who use this workflow before building.
Hypothesis 2
Ensure all products have detailed and consistent descriptions.
Assumption to check: Inconsistent product descriptions
Validate with people who use this workflow before building.
Hypothesis 3
Optimize images and data fetching for faster load.
Assumption to check: Slow loading times in certain areas
Validate with people who use this workflow before building.
Hypothesis 4
Add more payment methods like Google Pay or PayPal.
Assumption to check: Limited payment options
Validate with people who use this workflow before building.
App evidence
Original App Store material. Ratings and screenshots describe the existing app, not proof of demand for your version.
App Store description
Back Market is the best marketplace to snag premium quality refurbished tech like smartphones, laptops, game consoles, and tablets at up to 70% less than brand new. Better for your wallet, better for the planet. With our app, you can: • Shop for refurbished tech • Keep tabs on all your orders • Save your fave devices • Track price drops • Assess your tech for trade-in Buy refurbished devices from certified refurbishers with the Back Market app. • Every device comes with a free 1-year warranty • Free shipping on every order • 30 days to change your mind • Track your order in app • Pay for your device in installments • $20 off for college students or educators • US military: Add an extra −10% discount Devices sold on Back Market are up to 70% less than new year-round. Plus, our quality charter means our refurbished tech is a grade above other marketplaces. For anything else, our in-house customer service team is ready to chat, 6 days a week. Whatever you’re looking for, we’ve got the (refurbished) goods. • Apple favorites: iPhone, iPad, MacBook, Mac, Apple Watch, AirPods • Top-brand smartphones, laptops, tablets, audio, game consoles, home appliances and more Trade in your unwanted tech for cash with Back Market Trade-In. It’s easy! • Sell your smartphone, tablet, gaming console, speaker, or headphones • Receive an offer in minutes • Shipping covered by Back Market • Get cash money in your bank account within 6 business days from receipt of your device. Make sure your tech is giving 100 Use Back Market’s in-app assessment to test your phone's functionality. You’ll get a rundown of these key metrics in seconds. • Network and connections (3G, 4G, GPS, Bluetooth, and Wifi) • Audio and video performance (microphone, speakers, camera) • The screen (touch, multitouch, brightness, color, 3D Touch) • Sensors (Touch ID, Face ID, Gyroscope, Accelerometer) Choosing refurbished helps out your wallet — and the planet. Refurbished tech has up to 92% less of an impact on the environment compared to brand new. More questions? We’re just an app away.
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Screenshots
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Build scope
Plan a focused first version with your coding agent. These are planning assumptions, not a delivery guarantee.
Define the first version
Choose one audience and one core workflow. Use the kit to agree on its screens, data, and acceptance criteria before building.
Set boundaries
Decide which secondary features, integrations, and platform support can wait. Your version does not need to reproduce everything in the original.
Check the hard parts
Validate external services, specialist technology, data access, and ongoing costs for your chosen scope.
SUGGESTED BUILD STACK
React Native
Expo
Zustand
Supabase
React Navigation
React Native Reanimated
BUILD KIT DIFFICULTY
Expert
From the Build Kit assessment.
A reliable timeline needs an agreed scope and a technical check. Ask your agent to estimate the phases in BUILD_PLAN.md after that review.
