Have you signed up for TSA’s PreCheck program yet? If you do, you may be in for a surprise when you go to the application center to get fingerprinted and have your documents reviewed. Some of the sites are in strange places – as I found out when researching this story for my At the Airport column on USA TODAY.

The Transportation Security Administration is dialing down its program of “free samples” for passage through PreCheck lanes at airports.

Soon the only way to way to guarantee the buzz that comes with keeping your shoes on and your laptop and 3-1-1 baggie in your carry-on at the checkpoint will be to pay for it.

You can do that now through one of the Trusted Traveler Programs offered by U.S. Customs and Border Protection or by paying TSA $85 and visiting a designated application center for fingerprinting and document review.

That’s where things can get interesting.

In 2013, TSA adjusted its contract with MorphoTrustUSA to include the operation of what is now more than 300 (and counting) PreCheck application sites. Twenty-eight of those sites are currently in airports (LAX and ATL each have two) but for efficiency, many of the other PreCheck processing sites are in locations where Morpho was already doing credentialing for transportation workers at airports and railroads, and for truck drivers who haul hazardous materials and access port docks.

Penny Watermeier works for a travel management company in Omaha and was sent to an office in a suburban complex to complete her TSA PreCheck application.

“There were three other people there when I went,” said Watermeier, “Two were doing blood samples for the railroad and there was one other PreCheck candidate. I was in and out of the facility in less than 15 minutes and received my known traveler number within 10 days.”

Declaring the process “seamless and painless,” Watermeier also took the opportunity to do some shopping at Costco, which was across the street.

There was no Costco in sight when Bill Chandler and his wife drove from their home, an hour south of the Tallahassee Regional Airport in Florida, to Valdosta, Ga., to complete the TSA PreCheck process.

“We knew a good restaurant in Valdosta, so being retired, we decided to take a two hour drive, do whatever TSA needed and have lunch and come home,” he said via e-mail.

They imagined a nice day trip, but once they pulled up to the address Google maps directed them to, “We could hardly believe what we saw. We thought it was a scam,” said Chandler.

The couple backed out, drove around, checked their coordinates, and determined they were indeed in the right place.

“We walked in and a child was wailing in a back room. My wife went back and checked to see if the child was OK and I got in line with truck drivers getting permits to haul hazardous materials.”

While a bit unconventional, it was no scam.

“The process was easy and the lady was nice and we promptly received our TSA PreCheck approval in the mail,” said Chandler.

A study of sites listed on the Department of Homeland Security Enrollment Center Locator reveals other convenient, but seemingly non-traditional sign-up locations.

In both Knoxville and Johnson City, Tenn., the enrollment center is inside The UPS Store.

Helpful directions for the enrollment center at the River Wall Mall in South Charleston, W.Va., alert drivers to the fact that the mall entrance is “between Burger King and Krispy Kreme Doughnuts” and that they’ll pass a Mattress Warehouse before arriving at the front door.

In Moline, Ill., travelers and truckers mingle with patients in the waiting room of Birdsell Chiropractic & Acupuncture Clinic.

“We were already doing drug screening and physicals for truck drivers and after sending in some billing we were approached about doing fingerprinting for hazmat and TSA PreCheck,” said company owner Melissa Birdsell in a phone interview between patients.

Because Moline is just a few miles from Davenport, Iowa – the home of a major chiropractic school – the area is densely populated with chiropractors. “So this is a soft way of meeting people in the community, getting some new patients and is better than doing free spinal screenings in the malls,” said Birdsell.

The opportunity to get his company’s services in front of thousands of potential new customers is also what made Mark Hultquist, owner of Computer Renaissance in St. Cloud, Minn., say yes when MorphoTrust came calling in 2008.

“They were moving to computerized fingerprint instead of the old style of fingerprinting with ink and probably approached us because we were a computer store and would be familiar with that technology,” said Hultquist.

Above the fee his company receives for processing PreCheck and other applications, “these programs bring more than 2,000 people a year through our door who would not otherwise even know we exist.”

That cross-promotion of services also works to the advantage of the South Lafourche Library in Cut Off, La., which is located in a former Walmart building that also houses the parish government office that processes PreCheck and other programs used by many of the offshore oil and gas workers that work out of the nearby port.

Although the Enrollment Center Locator points applicants to the library, “our job is to help people and give information, so we’re happy to redirect them to the correct office,” said librarian Katina Gaudet. “But sometimes people who come in here for directions also go home with a library card.”

Since December 2013, when TSA began allowing passengers to passengers to enroll in TSA PreCheck for a fee, close to 475,000 people have signed up, with an additional 4,000 people joining each day, according to the TSA.