These jobs might be good to consider if your protagonist is an amateur detective who keeps getting pulled into investigating mysteries. Diane Mott Davidson has done it with a caterer. Nancy J. Cohen writes the Bad Hair Day series, set in a beauty salon.
Then, too, they might be useful for a romance series. And of course, with the right framing, they could be historical. Here, in no particular order are jobs that involve meeting new people.
Teaching a Hobby or Recreation Class
Think free offerings at a library, or adult education classes such as those offered by the Shepherd Center in Richmond. These jobs bring together people who are like-minded, and often of similar ages. Teaching a memoir writing class would bring a whole different demographic from coaching a Little League team. I’d put running a summer camp in this category as well.
Private teaching and tutoring provides slightly different opportunities. Students tend to be either extremely interested or extremely disinterested in the subject. Tutoring sessions or private lessons are often held at the home of the student or the teacher, in what can be a very personal setting. Although each teaching session involves only one student at a time, a professional tutor could have a string of pupils coming through the house all day.
Coffee shops have been done, but there are lots of jobs in food service, especially in small, local eateries. A broad range of people could be customers, perhaps mostly business executives who work nearby leading to international plot twists. It’s also a place where one’s protagonist can keep abreast of what’s happening in the neighborhood—where anything could be happening.
Perhaps instead of an amateur detective, your protagonist is a Good Samaritan, who publicly or secretly helps those in need. Think about the cook/chef and what food suppliers, etc., make up that circle. An independent eatery is going to have entirely different customers and employee needs than a sub-department within a larger grocery or department store. And don’t forget bartenders, who hear everything the drunk patrons blurt out.
A Book Store
Yes, book store mysteries are already out there. But consider a specialized book store—e.g., plants and gardening, or comic books—and what that clientele might be. Or reverse it: an avid collector of XYZ books who uncovers nefarious goings on in the business, or who strives to save a struggling indie.
Here again, there are options for a protagonist who is an employee OR a patron. What about the trials and tribulations, and conflicted feelings, of an employee who isn’t really fit. The local gym is a good place to learn about runs, walks, and other sports events in the area—where anything can happen. Remember the Boston Marathon bombing.
Fancier gyms might also include personal trainers, a pool, a bar, massage therapists, group fitness teachers, even towel valets. All of these services mean extra employees and usually higher membership fees. Because of the high degree of physical contact involved in many of these jobs, a gym employee may develop unusually close relationship with patrons.
I mean, really, just count the ways depending on what sort of retail. The pay typically isn’t very good, which could add a whole lot of motivation to pick up other work on the side. The majority of people currently working in retail juggle two or even three jobs to be afford basic necessities. Employees working on commission typically make even less but have to behave very differently at work.
A whole different set of options here. I’ve written a series of stories about a prostitute during the Civil War who unraveled the mysteries of all sorts of deaths. A modern version of that is one option. Then, too, the danger is a big factor. Whether prostitution is legal or not, there is an inherent vulnerability in such a position for any character. Suppose your sex worker is generally a good person, working to support family, and is friends with someone in law enforcement. Consider the threats to life and limb. What if your protagonist is the CEO of a ring of workers and gets involved in all sorts of things to keep the workers safe and healthy.
Prostitution was legal and regulated in France throughout the nineteenth century. When Napoleon become Emperor in 1804, he ordered the registration and fortnightly health inspection of all sex workers in the country. Brothels had to be owned and operated by women. In 1883, there was even a tourist guide to the best brothels and prostitutes in Paris, discreetly published: The Pretty Women of Paris.
Real Estate Agent
Need I say more? Keys to lots of empty houses which might house virtually anything. Going into residences alone with strangers. Etc., etc., etc.
Plumbers, roofers, electricians, etc. are in the unique position of working in the houses of complete strangers. Both the customer and the worker have to assume some level of trustworthiness on the part of the other. Customers open their homes to strangers who drive recognizable but easily faked vehicles, carry cases of tools (weapons), and usually go into the less-public areas of a home. Repair workers walk into the home of a complete stranger where anything might be seen or overheard, particularly from crawl spaces, attics, cellars, and other perfect spots to hide a body.
Nearly every job on this list has been moving to gig work in recent years, at least in the US. Employers of large businesses encourage workers to accept part-time positions, which almost never offer benefits. Teachers, professional trainers, bartenders, caterers, home repair workers, real estate agents, and especially sex workers are increasingly self-employed.
Many people working these positions as “gigs” have more than one occupation. Ride-share drivers, delivery drivers, salespeople, musicians, writers, editors, artists, beauticians, pet sitters, interior decorators, fashion designers, childcare providers, cleaners, translators, lawn care, etc., etc., etc., I have a friend who is simultaneously a retail worker, a music teacher, a gig musician, a translator, a language tutor, a florist, and a nanny, depending on what day of the week it is. Imagine the variety of interactions a character working multiple part-time jobs might have.
Bottom line for writers: And job or situation that brings your character into contact with lots of people is ripe with opportunities. Think outside the box!