I live in one for 7 months when I was seconded to a coastal office about 17yrs ago. Although it was connected to all the mains supplies inc gas.
My main gripe was the difference in temperatures. In hot weather it was a sweatbox & when it dropped cold then I had the heating on and it was burning gas constantly as it maintained the temp due to draughts from the various anti-mould vents.
Other things to consider:
The walls on those things tend not to stop a lot of sound in both directions.
Generally there are no clothes washing facilities beyond the kitchen sink
The washing facilities (shower, bath if you're lucky) tend not to be that great
Space, imagine yourself being confined to your upstairs 24/7
Utilities - Water, waste and Electric will need connecting. You can get gas connected but also you could survive on bottles, though you'd need to be on the ball for when it runs out regarding replacements. I'm not sure if you'd be able to have a landline for internet fitted so you're gonna be stuck with mobile options, which inexplicable in this day and age are still limited.
I lived solo & the utilities except internet but we weren't so connected like now so I was fine and I reckon, like
@amigafan2003 , if you're just a couple you'd also be ok