I am using Obsidian for some important notes every day.
I moved from Evernote to Obsidian.
From Day 1, my only worry has been
I prefer a free alternative/option for now, before I plan to upgrade once I am sure that obsidian suits best for my work.
Obsidian stores all related data to a vault in that folder, so if you just do a copy of that folder you’ve got a fine backup. This would of course still be on your local device, so if it fails it’s lost.
But given a laptop you could create a routine to copy the folder out onto a memory stick (USB stick/device) for safe keeping, or to another laptop of your choice if you’ve got something available.
You could also do various variants over the theme copying the vault folder to Dropbox, One Drive, Google drive, … Choose your potion… 
Note that I’ve so far talked about copying your vault to either of the backup related devices. It’s not recommended to keep/work with your vault directly towards Dropbox, One drive, Google drive, and so forth, as that might cause issues down the road related to file synchronization and what’s stored locally or not. I’m not going to go into the details, but be wary of this issue. Copying to either of these though is safe.
And you can also setup free synchronization alternatives to either of them, just be a little careful to sync towards the external device. I do also believes there are various free backup services online which should be OK to use.
There are loads of stuff to say on this topic, but it should be very doable to set up free backup/sync to keep your vault safe in case of device failures.
See also:
GitHub Desktop with git (not automatic, but Obsidian Git can be made so) is great to see the difference on changed files before you upload to the cloud (push to the remote; you need to learn some different wording with git). It’s free. How safe? In today’s world if someone says “safest”, I’ll let you finish the sentence…