Mortgage Sweep Dashboard

Overview

This tool runs parameter sweeps across mortgage scenarios — varying points paid, down payment, and target monthly payment — and lets you visualize the tradeoffs. There are three tabs: Analysis for charting loaded CSVs, Balance Over Time for plotting amortization curves, and Run Sweep to generate new results directly in the browser.

Quick Start

Balance Over Time Tab

• Scenarios are listed sorted by total lifetime cost (cheapest first). Each shows rate, down payment, points, payoff years, and total cost.
• Click any scenario to toggle it on/off. Selected scenarios each get a distinct color and are plotted as amortization curves.
• Best 5 (cost) auto-selects the five lowest total-cost scenarios. All selects up to 20. None clears the selection.
• Hover the chart to see the exact remaining balance for each scenario at any month. X-axis tick labels show year markers.
• The chart re-simulates the full 360-month amortization in the browser, including dynamic PMI cancellation and target-based extra payments.

Sweep Parameters

• Points % of Loan — enter whole numbers. -1 = 1% lender credit (reduces closing costs, raises rate). 2 = 2 points paid (reduces rate, increases closing costs). Range is divided by 100 automatically.
• Down Payment % — whole number percentage of purchase price. 10 = 10% down. PMI applies below 20%.
• Target Monthly Payment — total you want to pay each month. Extra above the base payment (P&I + escrows + PMI) goes to principal. When PMI drops off, that savings automatically becomes extra principal to keep you at your target.

Filters

• Filters apply to any output field. Supported operators: lt le gt ge eq ne
• All filters must pass for a row to appear in results.
• Common filters: funds_needed lt 60000 · payoff_years lt 20 · pmi_dropoff_month lt 48

Loading External CSVs

Drop any sweep_results.csv produced by mortgage_sweep.py into the sidebar on the Analysis tab. Multiple files load side by side — each gets its own color. Use Color By → CSV File to compare runs.

Key Output Fields

• total_cost — total interest paid over loan life + points cost. The truest apples-to-apples comparison.
• funds_needed — cash needed at closing: down payment + closing costs + prepaids − earnest money.
• pmi_dropoff_month — month when balance falls below your LTV threshold and PMI cancels.
• payoff_years — how long until the loan is fully paid off, accounting for extra payments.
• start_payment — total month-1 payment including PMI and any extra.