So this was a service based online business, not software, but I thought it was worth mentioning. Got about a hundred hot leads in the first day from a single Facebook post. It was something like "If you're interested in [service], comment below for a free sample." The comments boosted the visibility of the post exponentially, so we had about 100 replies a few hours later, all hot leads. Took a day or two to fulfil the free samples, and it led to years of passive income.
Maybe a dozen of those became customers right away, and then it was word of mouth from there.
Another commenter mentioned finding relevant forums on Reddit, it's the exact same idea.
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