Funding Buy and Hold Rental Properties - Beginner

[Trey Read]

I am 22 years old and looking to start investing in SF rental properties. 

With a Full-time job making 57k salary, a low down payment, what would be the best way to finance properties initially? 

Also What would be the best way to keep purchasing additional buy and hold properties (e.g. line of credit on other assets)?

Private lending? Mortgage? 

Thanks!