If you are in the United States, each state government maintains a registry of businesses in that state. Do a Google search like this: "register business georgia" (or whatever state the business is in.) For many states, you can look at the business records on line; in some, you'll have to go to a government office. That will tell you who owns the business and may provide other details. I suspect, but do not know, that most other countries have similar registries.
Many people, including a member of my family, have no Internet presence. It just doesn't seem important to him; nothing sinister about it.
If you are concerned that someone may be a "government agent" because you're thinking about buying or selling something illegal, don't do it. Even if the business owner is an honest crook, it's a pretty safe bet that law enforcement knows about any illegal businesses operating on the Internet. Try a search for "silk road."
If you are concerned that you will be cheated in an otherwise legal transaction, do a search for the business name. Businesses that cheat people turn up in reviews all over the place.
