Monetizing a subreddit with 40K members requires leveraging the audience without breaking Reddit's rules. I've seen success with affiliate marketing, promoting relevant products or courses, and earning around $500-$700 per month with a similar-sized subreddit. To increase earnings, focus on building a mailing list and offering exclusive content or discounts to subscribers, which can boost earnings to $2,000-$3,000 per month. Selling the account is possible, but be cautious of Reddit's terms of service, and expect to get around $5,000-$8,000 for a subreddit of this size, depending on engagement and niche relevance.