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
Loan Calculator Pro
Loan Calculator Pro is an easy to use financial calculator
$0.99 · In-app purchases
PRICE
$0.99
In-app purchases
BUSINESS MODEL
Paid
No overall Grossing estimate available
RATING
★ 4.6
25 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.
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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 included16 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 Loan Calculator Pro: 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
Allow users to save their custom loan scenarios.
Assumption to check: Limited customization options for loan calculations
Validate with people who use this workflow before building.
Hypothesis 2
Provide graph/chart visualizations of payment breakdown.
Assumption to check: No visual representation of amortization schedules
Validate with people who use this workflow before building.
Hypothesis 3
Enable exporting calculations and schedules to PDF or CSV.
Assumption to check: Lack of export options for results
Validate with people who use this workflow before building.
Hypothesis 4
Introduce reminders for loan payments and financial tips.
Assumption to check: Minimal user engagement features
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
Loan Calculator Pro is an easy to use financial calculator. Within seconds, you will be able to calculate the monthly payment for different types of fixed rate loans such as home mortgage, auto, and credit card. You can calculate "what if" scenarios to determine how additional monthly and yearly payment will help you to pay off your loan earlier and save money in interest. In addition, you can use Loan Calculator Pro to track all your extra payments at any amount and at any point in the life of your loan. FEATURES * Early Payment Simulation See how much interest you will save and how early you will pay off your loan by entering extra payment amounts per month and/or per year. * Extra Payment Tracking - Loan Calculator Pro will let you track all of your extra payments in variable amounts throughout the life of the loan. For example, it will let you track an extra $100 in principle on the first payment, an extra $300 on the 5th payment, and an extra $1000 one the 10th payment, etc. This way, the application will still be useful long after you have purchased your property and will let your know exactly where you are with all your loan payments. * Fast Calculations - Loan Calculator Pro is designed to be fast. Calculations are done instantly after you enter each amount field. * Large Numeric Keypad - The large keypad allows for easier, faster, and more accurate entry of numeric amounts. * Amortization Table - A complete payment schedule allows you to view the amount, interest, principal, and remaining balance for each and every payment of the loan. * Bookmark of Payments - You can bookmark the current payment you are at in the amortization table and the application automatically scroll to the memorized payment the next time. * Saved Loans - Loan Calculator Pro lets you save and organize all your various loans in a list so you do not have to enter the information over each time. It will also remember and opens up the last saved loan you worked on. * Loan List Reordering - You can reorder the loans from the saved list in any order you choose. * Email Export - Export loan information and payment schedule via email. * Passcode Security - Passcode protection to keep your loan information private. * Backup / Restore - Backup your data to your computer for safekeeping. Then restore it to your iOS device when you need to via the iTunes file sharing interface. * Intuitive User Interface - Special attention was given to the user interface to ensure that it is clean, intuitive, and easy to use.
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 Native
Expo
react-native-paper
@react-native-async-storage/async-storage
react-native-share
expo-router
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.
