Which add-on services make home inspectors the most money?

A standard home inspection leaves these services out by design. The InterNACHI Standards of Practice say the inspector is not required to determine the presence of mold or radon. Wells, septic systems, pools, and spas are left out too. The 2014 ASHI Standard in force excludes wood-destroying organisms, molds, and recreational facilities in the same way.

ASHI's revised Standard, approved in January 2026, names the category. It defines an additional inspection service as a specialized inspection outside the scope of a home inspection. Such a service, it adds, "may require additional licenses, certification, or training." That last part is what decides which add-ons a new inspector can offer. For how the two standards compare, see home inspection standards of practice.

Add-ons raise what each appointment earns without raising the base fee. That matters, because the base fee is the number clients compare when they shop. For how that base fee gets set, see how much a new home inspector should charge.

Radon is a radioactive gas that seeps into houses from the ground. The EPA calls it the second leading cause of lung cancer overall and the leading cause among people who have never smoked. Its Home Buyer's and Seller's Guide to Radon tells anyone buying or selling a home to test. It sets 4 picocuries per liter (pCi/L) as the level to fix. Real estate tests, it says, should run at least 48 hours.

The same guide says many states require radon professionals to be licensed, certified, or registered. Some real examples:

• Illinois requires a radon license under the Radon Industry Licensing Act. Applicants take an approved course and an NRPP or NRSB exam.
• Florida law says no one may take part in radon measurements unless the Department of Health has certified them.
• Maine has no home inspector license, but anyone who tests for radon must register with the state. See Maine.
• Pennsylvania law says a home inspector may not do radon work without that separate license. See Pennsylvania.

Where a state has no rule, the EPA points to two national credentials: the National Radon Proficiency Program (NRPP) and the National Radon Safety Board (NRSB). Radon is also the easiest add-on to explain. The health reason is clear, and the time on site is small. For the course, exam, and state rules, see how a home inspector gets certified to test for radon.

In several states, a termite report needs a pest control license, and a home inspector license does not cover it. Three examples:

• In Florida, a wood-destroying organism inspection for a real estate deal is made by a pest control licensee or its qualified representative.
• In Texas, an official wood destroying insect inspection is done by a licensed applicator or technician in the termite category, through the Texas Department of Agriculture.
• In California, no report on wood-destroying pests goes out until a Branch 3 field representative or operator has inspected the property.

Some inspectors earn the pest license as well. Others refer the work to a licensed pest company. For the license each state names and when lenders ask for the report, see can a home inspector do termite inspections.

Sewer scope. A camera on a cable runs from a cleanout toward the city main, showing the inside of a line no home inspection sees. ASHI's revised Standard lists drain and sewer cameras among the tools an inspector is not required to use. No state license for the work turned up in the sources checked for this page. Training is offered by groups such as InterNACHI, which runs an online course and a one-day hands-on class.

Mold. Sampling means lab fees and, in some states, a license. Florida bars anyone from performing a mold assessment without meeting its mold assessor rules. New Hampshire requires a national third-party certification for paid residential mold assessment. Mold sampling fits when the inspection finds moisture, staining, or a musty odor. It is not a default add-on.

Wells and septic. State law can set the test. In Oregon, a seller who accepts an offer must have a domestic well tested for arsenic, nitrates, and total coliform bacteria. Oregon also limits septic evaluations to people such as professional engineers, registered sanitarians, certified installers or maintenance providers, and NAWT-certified inspectors. Inspectors in rural areas often offer these through a qualified partner.

Russ's advice is to mention each service when the client books, as information rather than a sales pitch. Say what it checks and why it fits this house. A buyer of a 1955 house in a neighborhood with known sewer line problems does not need a pitch. The buyer needs to know a sewer scope exists and why it matters. That conversation does the selling.

Count the costs before adding one: equipment, lab fees, licensing, and the extra time on site and in the report. For how add-ons change a working day, see how many inspections you can do in a day. For narrower lines of work, see home inspector specializations that pay.