@Mondo Guti, I did a lot of renovation projects on my first home (primary residence), so 2007. First property bought specifically for investment was 2011 with a bank REO property. This would be called a BRRRR now, but like Michael mentioned, BRRRR wasn't a think 10 years ago. First purpose bought flip was in 2015.
Or you can dial it back to 1988, when I watched and "helped" my dad finish our basement himself. I was 6 yrs old so my help was limited to giving my dad the wrong tools.
Personally, I don't think you need to know everything, but understanding basic construction process, ball parking costs, and finding or having good contractors all helps the process.