sub-network? - new premises. What would you do here?

[16k_zx81]

I am moving into an office next week with a shared internet connection.

Please help me with a sanity check on the following (networking is not my forte)

For the sake of customers privacy, and to protect other computers on the network, I am thinking a sub-network would be the best approach.

Q1. Do you see these concerns as relevant? (would you do this yourself if you were doing computer repairs as a member on a larger network?)

Q2: Is this the best approach in these circumstances?

Q3: What would be the easiest way to go about setting something like this up (or alternative?)?