Your First 90 Days: The Essential Resale Home Checklist

Why it matters

The first 90 days are critical because you are transitioning from a general home inspection—which is a point-in-time snapshot—to active management of complex systems. Addressing immediate maintenance items can prevent minor issues, like a slow-dripping P-trap, from becoming $10,000 mold or structural repairs. Furthermore, setting a baseline for your HVAC and plumbing systems during this window can reduce your annual energy costs by ensuring everything is running at peak efficiency rather than struggling against years of the previous owner's neglect.

How often

While this specific guide focuses on the one-time transition of the first 90 days, many of these tasks will move into your recurring maintenance schedule. Safety checks (smoke detectors) occur every six months, while air filters and water filtration systems are typically serviced every 30 to 90 days.

What you need

• Tools: Cordless drill, screwdriver set, adjustable wrench, pliers, flashlight, and a ladder.
• Safety Gear: Work gloves, safety glasses, and N95 masks (for attic/crawlspace work).
• Supplies: New HVAC filters, smoke/CO detector batteries (or new units), fire extinguishers, and "deep clean" supplies (vinegar, baking soda, heavy-duty degreaser).
• Documentation: Your home inspection report and a dedicated folder (digital or physical) for receipts and warranties.

Step-by-step: The 90-day roadmap

Phase 1: The Safety Baseline (Days 1–7)

1. Change the locks: You have no way of knowing how many copies of your keys exist. Replace deadbolts or rekey the cylinders on all exterior doors.
2. Audit life-safety devices: Test every smoke and carbon monoxide detector. If they are more than 10 years old (check the date on the back), replace the entire unit. Install at least one fire extinguisher on every floor and in the kitchen.
3. Locate main shut-offs: Find the main water shut-off valve and the main electrical breaker. Label them clearly. If the water valve requires a "curb key" (common in some regions), purchase one and keep it nearby.
4. Reset garage codes: Clear the memory on your garage door opener and program your own remotes and keypad codes.

Phase 2: The Efficiency Reset (Days 8–30)

1. Service the HVAC: Even if the inspection said it works, change the air filter immediately. Vacuum out the registers and check the outdoor condenser unit for debris.
2. Clean the "invisible" lint: Standard move-in cleaning often misses the dryer vent. A clogged dryer vent is a leading cause of house fires and forces the machine to run longer, increasing your electric bill. Use a brush kit to clean the entire length of the duct to the exterior wall.
3. Set water heater temperature: Check your water heater’s thermostat. Setting it to 120°F (49°C) is generally sufficient for household needs, prevents scalding, and saves on heating costs.
4. Flush the drains: Run hot water and baking soda down all drains to clear minor odors and build-up left by the previous occupants.

Phase 3: The Observation Window (Days 31–60)

1. Monitor the Attic/Crawlspace: After the first heavy rain, go into the attic and crawlspace with a flashlight. Look for active leaks, damp insulation, or pooling water that the home inspector might have missed during a dry spell.
2. Check the Grading: Walk the perimeter of the house during rain. Ensure water is flowing away from the foundation and that downspouts are discharging at least 3–5 feet away from the walls.
3. Test GFCIs: Push the "test" and "reset" buttons on all GFCI outlets (usually found in kitchens, bathrooms, and garages) to ensure they trip and reset properly.

Phase 4: Long-term Planning (Days 61–90)

1. Inventory the Roof: Use binoculars to check for cracked shingles, rusted flashing, or moss growth. Do not walk on the roof yourself unless you have proper safety equipment.
2. Prune Overhanging Limbs: Cut back any tree branches that are within 10 feet of your roofline to prevent squirrel access and mechanical damage to shingles.
3. Create your "Pro" Shortlist: By now, you likely know which systems are "fussy." Research and vet a local plumber, electrician, and HVAC technician so you aren't scrambling during an emergency.

When to call a pro

• Electrical Sparks or Humming: If you hear buzzing from the panel or see charred outlets, call an electrician immediately.
• Gas Smells: If you smell "rotten eggs," leave the house and call the utility company or a licensed plumber.
• Major Structural Cracks: If you notice new cracks in the foundation or drywall that are wider than a quarter-inch, consult a structural engineer.
• Main Sewer Backups: If multiple drains are gurgling or backing up, you likely need a professional sewer scope and clean-out.

Safety

• Circuit Awareness: Never overload a single circuit with high-draw appliances (space heaters, vacuums) in an older home with legacy wiring.
• Ladders: Always maintain three points of contact when climbing to check gutters or detectors.
• Chemical Mixing: Never mix ammonia and bleach when deep-cleaning your new kitchen or bathroom; the resulting gas is toxic.

Cost

Early maintenance is relatively inexpensive compared to emergency repairs:

• Rekeying locks: $75–$200 for a locksmith, or $20–$50 per lock for DIY replacement.
• HVAC Filters: $15–$40 depending on MERV rating.
• Dryer Vent Cleaning Kit: $20–$30 (DIY) or $100–$200 (Pro).
• Safety Kits (Detectors/Extinguishers): $150–$300 for a standard 3-bedroom home.
• Professional HVAC Tune-up: $100–$200.