Accessing 4TB WD SSD from both home and office via high-speed fiber

I am helping a friend set up her "new" system once she moves into her new office, located in a separate building (20 feet away), adjacent to her home. She has high-speed fiber from the primary modem to both the house and the office.

She has all new equipment: M4 Mac mini with 2 TB, 24 GB of RAM; 27" wide screen; 4 TB WD SSD as her central storage with backups both in-house and in the cloud; Logitech Stream camera and using a Cal-Digit 3 to sort.

My questions:

If I connect the WD 4 TB directly to the fiber, will she have access to that both in the office and at home with her MacBook Pro via wifi?

She currently uses her MacBook Pro for all her storage (backing up to her iCloud account and occasionally to a portable Seagate), but she's running out of space. She is also expanding into teaching internet classes and plans to create a website and produce podcasts.

She is not "comfortable" enough to maintain a NAS system at this point, which is probably the best way to go. However, I am looking for a more immediate solution for her to move forward at this point.

She lives in a rural area where the power frequently goes out, so relying on cloud storage as the primary is not advisable. I like separating my applications from my data in case there is a problem with the Mac and I have no access or loss of data, even if backed up. If the Mac becomes unoperable, she could switch to using her notebook and have access to all her data from the 4TB drive.

Am I on the right track?

[Re-Titled by Moderator]

Original Title: New System set-up