I make $40K/month with this one website

Hit the problem himself (bank only gave PDF statements; he wanted years of data in Excel). Wrote a Kotlin console app for his own bank, generalized it by testing on his other banks and friends' banks, and had a friend build a Next.js UI. Built in about a week, bought a domain, launched, then bought Google Search Ads to send traffic. Shows it to the target audience, not friends and family ('they'll just lie to you'). If an MVP takes 1-2 weeks, just build it rather than validating first.

Ran Google Search Ads from launch for about 6 months and spent a lot of time optimizing campaigns for profitability.

Tried blogging and building in public on Twitter.

Sent cold emails for three months. Targets and volume not stated.

After cutting ads, every visitor was organic, so he could see 2-3 new sign-ups a day arriving on their own. From then on he focused on the product: fixed whatever customers complained about by email, and used analytics (drop-off pages, unused features) to decide what to build or stop building. Advises skipping social media pages and followings entirely and focusing on the product.

In the first two years, replied to customer emails as soon as possible, including dealing with a 3 a.m. email immediately, because each extra customer moved MRR noticeably.