More and more developers these days give their work away for free and create a Patreon. I don't know if it would work in this case, but if enough people got wind of the idea, perhaps it would at least equalize. Not all brilliant ideas are meant to be businesses, so why not give users the options to support something they find useful? You can easily thermometer the demand this way, and if there's a [community] need that you are fulfilling, supporters will show up. You can always hide more advanced features behind the Patreon subscription levels, too. It sounds like what you are really after is a community that vets health knowledge, and this could be one cornerstone of that.