Learn English – Very busy vs busier

A rule of thumb for this is that a "how" question addresses a topic with more specificity than a "what, like" question.

If I just escaped from prison and hitch-hiked a ride out of town, the driver might ask me "What is prison like?", meaning he would like a general description of prison. If he asked me "How was Prison?", then he is interested in my particular experience in the pen.

Generally, I would say using the "how" is the safer approach in most cases when you are asking about something specific. "How were your clothes after it rained? (Soaked!) and How is the new car? (Super-fast!) are both totally acceptable. Using "what.. like" will also get you by in some cases. "What were your clothes like after it rained?" is passable. "What is the new car like?" might invoke a weird or sarcastic response "Like a tiger beetle on wheels". It is still passable, but it might sound funny to certain people.

Another thing to consider is that a "How" question demands a description of the subject.

"What was it like" invites the responder to draw a comparison to something familiar to the asker.

For example "How was India?" and "What was India like?" could possibly (though not necessarily) invite different responses.

The first might be responded to with "beautiful, but very hot and humid", while the second might provoke a more comparative description. "It reminded me of Egypt, but more humid."

I am open to correction, but I hope this helped.

I think the perfect word might be turf, but it's informal.

turf
4. slang US the territory or area of activity over which a person or group claims exclusive rights

In an informal context, invade might be too formal. I would use step on: "Don't step on my turf and steal my customers!" It sounds tough to me.

Formally, you could use territory.

territory
1. a. An area of land; a region.
3. An area for which a person is responsible as a representative or agent: a salesperson's territory.

Neither word means "work area" by themselves. But in the right context, like the fictional one you have provided, I think the meaning is clear and what you are trying to describe.