I have seen many natural weed killers on Pinterest. Most of them had multiple ingredients that I didn't feel like shopping for.
So, I decided to try just one ingredient. The next day I checked my patio, and the weeds had shriveled up and died. I was excited because it would not hurt my animals.
Fill a squirt bottle with distilled white vinegar. Spray on the weeds. The next day repeat if necessary.
There you have a super cheap, super safe, weed killer.