Luck mainly. I didn't go to university (I live in the UK) after school but was lucky enough to still get a good job at 19. Just knowing how to use a computer opened a lot of doors back in the day.
I'm kind of an introvert and was a pothead when I was younger so didn't go out much and was single when I lived at home. That let me save up a lot of money without really trying. My parents did help a little when I bought my first house at 22 as well.
I live in an area with some of the lowest house prices in my country and the house I bought was very cheap. It was a bit fucked but kind of livable and I had big plans to get all kinds of work done over the years and have it sorted out and paid off by the time I was 47.
Bit off way more than I could chew. There was no central heating, a coal cellar that was completely open at the front and damp all over. It was freezing during the winter and sweltering in the summer.
I got a new kitchen and bathroom put in and some of the stuff I had planned done but I'm not handy in any way and had to pay other people to do the work. I realised that doing it that way would be more expensive than just selling up and buying a new place with a lot of that stuff already done.
The house was so bad I actually sold it for the same price I bought it for 12 years later. But, the money left over after paying that mortgage off more than paid for the deposit on another house last year.