Overall it was a great learning experience, but incredibly challenging. There was nothing like OP's guide (or HN, or Google for that matter), so the knowledge had to come from books, Usenet news, and mail lists. It helped that we had experience managing Unix servers and WAN networks at the University, but still had tons of things to figure out, from setting up dial-up lines, to keeping httpd servers up and running (we decided to use Linux 0.99 beta from the get-go, but it kept crashing, usually in the middle of the night; later we discovered it was a race condition in the multi-serial port card driver, which manifested only when several ports were under heavy use, hence only happening at night).

Although we could solve most of the technical challenges, we were absolutely clueless on how to run a business: selling, bizdev, billing customers, hiring and building teams, etc. I have fond memories for those (usually bad) decisions, but can't stop thinking how things would be different if I could magically go back and do it all over again :)

We quickly reached a few thousand customers, and realized it was turning into a capital intensive business - phone lines in Brazil in the 90's were crazily expensive, plus Cisco routers, server upgrades, etc. We decided to pivot towards B2B, thus becoming one of the first corporate ISPs: web hosting, security consulting, leased lines, some web development.

We sold the company 5 years later, when the market started consolidating, right before the dotcom crash.

If it was intentional, great job :)