Technical Specification: Professional BRRRR Investment Calculator

Overview

A clean, professional, single-file browser-based application designed to assist real estate investors in modeling the "Buy, Rehab, Rent, Refinance, Repeat" (BRRRR) strategy. The tool performs real-time financial calculations to output cash-on-cash return, total capital required, and post-refinance cash flow.

Core Features

• Input Sections:
  • Acquisition: Purchase price, closing costs, rehab budget.
  • Operational: Monthly rent, property taxes, insurance, management fees, maintenance reserves.
  • Refinance: After Repair Value (ARV), loan-to-value (LTV) ratio for refinance, interest rate, loan term.
• Real-Time Analysis: Instant calculation of the "Total Cash Out of Pocket," "Post-Refinance Loan Amount," and "Remaining Equity."
• Visual Summary: Clean summary cards displaying key KPIs (Cash on Cash ROI, Annual Cash Flow, Break-even analysis).
• Responsive Design: Modular input groups that stack vertically on mobile devices and expand into a dual-pane view on desktops.

UI/UX Design

• Aesthetic: Modern SaaS design. High-contrast, clean typography (Inter or Roboto), generous whitespace, and subtle border-shadows for container elements.
• Color Palette:
  • Background: #F9FAFB (Cool Gray 50)
  • Primary Accent (Buttons): #2563EB (Bright Blue)
  • Results (Positive): #059669 (Emerald Green)
  • Results (Alert/Negative): #DC2626 (Red)
  • Cards/Containers: #FFFFFF (White)
• Transitions: Smooth fade-in effects for dynamic result updates. Subtle input focus animations (border color shift).

Technical Directives

• Single File: All CSS/JS must reside in the single HTML file. Use CDN links for any dependencies (e.g., Tailwind CSS via CDN).
• Sandboxed Environment:
  • NO LOCAL STORAGE: Do not attempt to save or retrieve data from localStorage/sessionStorage. All state must be handled in memory.
  • NO COOKIES: Do not store user preferences.
• Responsiveness: Use CSS Flexbox/Grid to handle window resizing without overflow issues.
• Interaction: Use vanilla JavaScript event listeners (input, change) to trigger re-calculations instantly as the user types, providing a fluid feedback loop.
• Accessibility: Ensure all input fields have explicit label tags and appropriate aria-labels for screen reader compatibility.

Layout Structure

1. Header: Title and brief sub-title explaining the utility.
2. Main Layout (Desktop):
   • Left Column: Input forms grouped by logical phases (Acquisition, Income/Expense, Refinance).
   • Right Column: Sticky summary panel showing high-level KPIs.
3. Main Layout (Mobile): Single column scrolling stack with the summary panel pinned to the bottom or top of the viewport for constant visibility.