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
ROI Calculator Cash Evaluation
Instantaneously see your ROI and Cash-On-Cash calculation results as you type in your numbers! Never worry again about remembering the formulas to calculate your investments, because this app does it all for you! Retu...
$1.99 · In-app purchases
PRICE
$1.99
In-app purchases
BUSINESS MODEL
Paid
No overall Grossing estimate available
RATING
★ 4.4
5 ratings · Top 30%
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.
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Build Kit
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A product spec, screen plans, and build steps for your coding agent.
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What's included14 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 ROI Calculator Cash Evaluation: map the core Finance 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
Add features like investment forecasting and comparison.
Assumption to check: Limited functionality for advanced calculations
Validate with people who use this workflow before building.
Hypothesis 2
Implement user accounts to save history and settings.
Assumption to check: No user accounts or data persistence
Validate with people who use this workflow before building.
Hypothesis 3
Include graphs or charts to visualize ROI trends.
Assumption to check: Lack of visual representation for ROI
Validate with people who use this workflow before building.
Hypothesis 4
Enhance UI with themes and customization options.
Assumption to check: Basic UI with minimal customization
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
Instantaneously see your ROI and Cash-On-Cash calculation results as you type in your numbers! Never worry again about remembering the formulas to calculate your investments, because this app does it all for you! Return On Investment formula? We've got you covered. Cash-On-Cash formula? Yep, that, too! As a bonus, an internet connection is NOT NEEDED to use this calculators in this app or to remember your last inputs. This gives you the freedom to crunch your numbers on the go: just start typing, and your results appear! This app is smart: If you're in the middle of a calculation and you answer a call, switch to another app—or even close the app—it will remember all of your input. So you can pick right back up where you left off. (Note: deleting the app will, indeed, erase your input) If you would like to see a specific feature implemented, please let us know in a kind app review. (Remember: please review apps based on what they are intended to do; not on what you wish they did. The absence of a desired feature does NOT equate to a negative app review.) Note: While the math formulas in this app are tested & accurate, any results derived herein are not to be considered CPA advice of any kind.
Written user reviews are not shown here. Check current App Store reviews >
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 Navigation
React Native Paper
React Hook Form
@react-native-async-storage/async-storage
Expo
Zustand
BUILD KIT DIFFICULTY
Starter
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.
