Started when I was a kid. We had a sand pit, (they used to haul sand/dirt from there as a business) behind our house. My friends and I used to go back there and ride our bikes. Not a whole lot to do there on a bmx bike, but we used to watch all the people riding their 3 wheelers, dirt bikes, and occasional Odyssey. We always dreamed of owning our own one day. To kick things off my friend got ahold of an old rear engine lawnmower which we quickly converted to off road use. New pulleys, belt, and ditched the deck. Eventually we got some used atv tires for the rear. Fastest we got clocked was something like 35mph. He then got a Honda ATC200X. Well, I really had started asking around at that point. I had a job (I was 14) and had a little bit of money. A coworker told me he had an old atv in his yard I could have! Turns out it was a Suzuki LT125 with 4 flat tires, busted pull rope, and no spark plug. 2 tires got tubes, got a new plug, and that's where I learned the value of getting actual pull start rope instead of regular rope from the hardware store. Pay the money and do it right. It was a great starter atv, but I always lusted after the atc's, finally getting my own ATC200S.
From there it would lead to more three wheelers from Honda and Kawasaki, dirt bikes, then back to atv's. Currently I have one of each (atv, atc, dirt bike) in my stable.