Griffen Bradds · Sonoma County Realtor
True Monthly Cost Calculator
See what a Sonoma County home really costs each month, beyond what Zillow shows you.
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Your True Monthly Cost
What Zillow Shows You
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Principal + Interest only
What You Actually Pay
$0
Everything included
The Gap Zillow Doesn't Show
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That's how much more you'll pay each month than the basic mortgage calculators suggest.
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Full Monthly Breakdown
Principal & Interest
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Property Tax
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Home Insurance (estimate)
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HOA
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Maintenance Reserve (1% rule)
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Utilities Estimate
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True Monthly Cost
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How we calculated this (sources and assumptions)
All numbers above are based on real Sonoma County market data, not generic Zillow defaults. Here's where each component comes from:
- Property Tax (1.1% default): Typical Sonoma County effective rate including Prop 13 base plus voter-approved bonds and special assessments. Source: Sonoma County Auditor-Controller-Treasurer-Tax Collector.
- Home Insurance (by fire zone): Estimates based on Sonoma County market data and Cal Fire Fire Hazard Severity Zone designations. Low ~$2,000/yr, Medium ~$4,000/yr, High ~$7,000/yr. Source: Cal Fire FHSZ Maps. Actual quotes vary by property, carrier, roof type, and defensible space.
- Maintenance Reserve (1% rule): Widely cited industry guideline for annual home maintenance budgeting. Source: Investopedia. Older Sonoma County homes (most of our housing stock) may need 1.5%.
- Utilities Estimate ($550/mo): Realistic Sonoma County household average. Includes PG&E gas/electric ($200-500), water/sewer ($80-200), garbage ($30-60), internet ($60-120). Source: PG&E typical residential bill + EIA regional data.
- Zillow Comparison: Based on Zillow's standard payment estimator methodology, which typically excludes maintenance reserves, utilities, and PMI.
Estimates are educational, not advice. For your specific scenario, consult a CalHFA-experienced lender, a licensed insurance broker, and a qualified tax advisor.
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