The base inspection fee is how most home inspectors get paid. Add-on services are how the best ones build income that separates them from the pack. Every add-on is a service your client genuinely needs, charged at the same appointment, without requiring another drive across town. Here is a detailed look at which add-ons generate the most revenue, which have the best value-to-time ratio, and how they stack up in the Pacific Northwest market.
Why Add-On Services Matter More Than Base Fee Increases
Many inspectors think about growing income by raising their base fee. That works to a point, but there is a ceiling. In a competitive market, pricing yourself significantly above comparable inspectors costs you referrals. Add-on services are different. They increase what you earn per appointment without pricing you out of the base market, because clients are comparing base fees when they choose an inspector, not the price of an optional radon test.
An inspector charging $450 for a base inspection with an 80 percent radon attachment rate and a 60 percent sewer scope rate earns dramatically more per year than an inspector charging $500 flat with no add-ons, even at the same inspection volume. The math on add-ons is powerful.
Radon Testing
Revenue potential
Radon tests add $125 to $175 per appointment in the Portland and Southwest Washington market. The incremental time cost is minimal. You deploy a passive canister or electronic monitor at the start of the inspection, pick it up after the required exposure period, and the lab delivers digital results directly to you and your client.
Why clients need it
Radon is a naturally occurring radioactive gas that seeps from the ground into buildings. It is the second leading cause of lung cancer in the United States. Parts of Oregon and Washington have elevated radon potential, and buyers of homes with slab foundations, basements, or lower-level living spaces are especially encouraged to test.
Attachment rate potential
Radon testing is one of the easiest add-ons to sell because the health case is clear and the price is modest. Inspectors who mention radon naturally during the booking call typically see attachment rates of 60 to 80 percent or higher.
Sewer Scope Inspection
Revenue potential
Sewer scopes add $150 to $250 per appointment. The service uses a camera on a flexible cable pushed through a cleanout to inspect the main sewer line from the house to the city main. You need to purchase or lease the camera equipment and learn how to interpret what you see, but the skills are learnable and the equipment investment pays back quickly at these prices.
Why clients need it
A failed sewer line is one of the most expensive surprises a buyer can face after closing. Replacing a main sewer line in the Portland metro area typically runs $5,000 to $15,000 or more depending on depth, length, and access. The problem is completely invisible to a standard home inspection. A sewer scope is the only way to evaluate line condition before purchase.
In older Portland and Vancouver neighborhoods, orangeburg pipe, cast iron in poor condition, and root intrusion are common findings. Buyers and agents in these markets have become increasingly aware of sewer scope value, making it one of the easiest add-ons to recommend.
Attachment rate potential
Sewer scopes attach at very high rates on older homes and in established neighborhoods. On newer construction, attachment rates are lower. Overall, inspectors who proactively recommend sewer scopes typically see 40 to 70 percent attachment.
Thermal Imaging
Revenue potential
Many inspectors charge $150 to $250 for a thermal imaging scan as an add-on. Infrared cameras reveal heat signatures that indicate moisture intrusion, missing insulation, electrical hot spots, and HVAC distribution problems invisible to the naked eye. An inspector with a thermal camera can find problems that no visual inspection can detect.
The alternative approach
At Trusted Home Inspections, thermal imaging is included with every inspection at no extra charge. This is a strategic choice rather than a missed revenue opportunity. Including thermal imaging as a standard service creates a powerful differentiator that competitors who charge extra cannot match. It also reduces liability exposure by finding things that standard visual inspection misses. For inspectors building a reputation in a competitive market, this approach often generates more revenue through referrals than the add-on fee would have produced.
Either approach can work. The right choice depends on your market positioning and how you want to differentiate yourself. Learn more about what thermal imaging finds and why it matters.
Mold Testing
Revenue potential
Mold testing adds $200 to $500 per appointment depending on the number of samples collected and the lab used. Air samples and surface samples both command different pricing. Results typically come back within 24 to 72 hours from the lab.
Why clients need it
In the Pacific Northwest, moisture is a constant concern. Crawlspaces, attics with poor ventilation, and bathrooms without exhaust fans are common breeding grounds for mold in Oregon and Washington homes. When an inspection reveals elevated moisture readings, visible staining, or musty odors, a mold test answers the question of whether a health risk is present and how serious it is.
Attachment rate dynamics
Mold testing is not a default add-on for every inspection. It attaches naturally when the inspection findings suggest moisture concerns. Inspectors who use moisture meters and thermal cameras find more situations where mold testing is a reasonable recommendation, which creates more opportunities to offer the service.
Well and Septic Inspections
In rural areas outside the Portland core and across parts of Clark County, properties on private wells and septic systems require specialized inspection services beyond the standard home inspection. Well water testing adds $100 to $250 depending on the panel of tests ordered. Septic inspections add $200 to $500 depending on whether a pump-out is involved.
Inspectors serving markets with rural properties who add well and septic services can significantly expand their revenue per appointment on those jobs. These services require additional certifications or partnerships with licensed septic professionals depending on state requirements.
What a High Add-On Day Looks Like
Here is a realistic picture of what a two-inspection day with strong add-on attachment generates:
Morning inspection on a 1960s home. Base fee $475. Radon test $150. Sewer scope $175. Total: $800.
Afternoon inspection on a 1990s home. Base fee $450. Radon test $150. Total: $600.
Two inspections. Total revenue for the day: $1,400. That is $700 average per appointment, well above what a base-fee-only inspector earns at the same inspection count.
Building Add-On Revenue Starts with the Booking Call
The most effective add-on approach is to mention each service naturally during the booking call or in your booking confirmation, not as a hard sell but as a professional recommendation. Tell the client what each service checks for and why it is relevant to this specific home. A buyer scheduling an inspection on a 1955 home in a Portland neighborhood with known sewer line issues does not need to be sold a sewer scope. They need to know it exists and why it matters. That conversation does the work.
For a full breakdown of how add-ons fit into overall income strategy, see Can You Make Six Figures as a Home Inspector? and How Much Do Home Inspectors Make?