For well under $100 you can buy a USB hard drive with plenty of space to back up one - if not two - computers. No paid subscriptions, no hassle, you can set your computer to automatically backup on whatever schedule suits you. I have two at 320Gb each, that cost around $69 each.
I would recommend keeping one at a location other than your home, such as at work, a relatives house, or at a friends house.
That way a fire or theft doesn’t negate your effort. I keep a backup drive at work and bring it home about once a month, backup everything, and take it back to work the next day.