Unless you're already famous, Stand Alone is a difficult nut to crack and make money in this Indie market today. It would take lots of bucks and lots of advertising unless you happen to get extremely lucky and hit some kind of viral sharing page. We know not where to find those, or even if it exists.
The best case for freebies that will turn into revenue - write a series, and once you're at three or four or five, post the first one as a freebie, and hope you entice readers to buy the others.
KindleUnlimited Freebie market is probably best place to get traction for a new author if you choose Free. You still earn a fee, and those readers that seek freebies (altho KU readers pay a monthly fee) have a gazillion to choose from, but is no less competitive than a Stand Alone book finding a reader audience.