Repeat investing, down payments

[David Huffmire]

I’ve listen to a lot of great podcasts about investing in multiple properties and growing a portfolio.  Which is exactly what I want to do. 
However, it takes me about two years to save up a 20% down payment enough for a small property in the south so my question is this, 

what strategies are being used by people to accumulate enough money to cover the upfront cost of each additional property in their portfolio?? because I’d rather not go at a rate of one property per two years. I’m in California and only looking to buy in the south where I can afford it.