I started in 2000. The key back then (which I didn't know) was knowing about type in traffic and pay per click which were big at the time. And the type of domains that would get traffic, or have the best future demand.
I think many people starting out back then, without the guidance of someone in the know, would just buy domains and hold to sell. And it's amazing how many people when starting (even today) will invent the crappiest made up names and think they are great. Instead of going for simple one and two word combos, or short letter or number domains, or short brandables, there was probably a lot of good stuff available to register or buy for $xx or $xxx in the aftermarket at that time. I remember on one site seeing loads of LLN.com going for $20 to $30 each.
Pay per click income was good 20 yrs ago and it could generate the income to renew your domains along with the odd sale. But you had to know it existed first, and then how to plug into it.
There was no easy to find domainer community then, no popular domain forums, you would only hear the odd story in the news now and then that such-and-such domain name sold for $500,000 or a million.
Also, in the early 2000's you could create a webpage or website, submit it to dozens of search engines, and actually get search engine traffic fairly quickly. Partly because there were a lot less websites then, and this was before Google dominated so much and search advertising became such big business.
My first clue about other domainers and a domain community was when I sold a one word .cc domain. A few weeks later I did a search on the domain I sold, and up popped a link to the weekly DNJournal sales report which had reported my sale. I remember seeing all the other sales reported, and articles on domainers, it was an amazing and thankful eye opening to the domain world, and reading about people and the domains they had.