Linux Questions

I am currently using GNOME Backups (aka Déjà Dup Backups) to backup all my files to a "backups" folder in my Dropbox. This is not a good solution - first because I want to stop paying for dropbox, second because I don't want to keep everything in the cloud, third because everything is stored twice on my laptop and storage is precious.

I therefore want to manage back-ups locally instead. I would like to keep using Déjà Dup, as it has worked really well and effortlessly.

My initial idea is very bare bones. I could keep an old laptop running 24/7, connect a hard drive, and use SSH file transfer in Deja Dup in order to store everything on that machine. That said, I have a few concerns as well.

1. Is this a good way of doing things? Should I be doing something else instead?
2. I'm not always at home - will it be a problem if the Backup software cannot find the folder because it's not on the correct network, or will it have the sense to wait until it's connected to the correct wifi?
3. Will the old laptop use a lot of power, or is it regrettable for any other reason? Is it possible to make it automatically hibernate for example during the nigthtime? Or to have it spend very little power unless anything is connected via SSH?
4. Would it be better to get a dedicated device, like a Rasberry Pi or something? I don't have all too much faith in my old laptop not making noise with the fan running at random times.

It looks like my partner will be getting a new laptop running Linux soon enough as she has to hand in her work computer, so it would be good timing to get a proper solution into place.

Thank you in advance!