Mechanical or SSD for offsite storage that’s updated at least yearly?

I have about 100gb and growing that is critical for my business. File size growth is slow, so it will be years and years before it even gets to 200gb.

I have multiple local copies and a copy in google drive, but I want to leave a hard drive at my mother-in-law’s house.

I only want 2.5 form factor or smaller as my mother-in-law will be carrying it here when she comes to visit us on the city.

I’m not sure what the recommendation is. I’m not a millionaire, I’m just freelance. So, I’d like to minimize cost.