What are different ways to partner with somebody?

[Jon Guy]

Thanks for reading!  First time poster but long time reader of the forums. I have a couple single family houses but I want to buy small multifamily properties. 

What are some different ways to partner with somebody? I don’t have the 20% down to keep doing deals and buy these small multifamily properties by myself or the cash reserves in my bank to get approved from banks. I don’t want to keep waiting 3 or 4 years for me to save up for a downpayment.  

How did people like Rod Khleif buy 800 single family homes? Or Sterling White with over 150 single family homes? I really don’t understand how they are doing that. 

If I have little to know money to put into these deals, but If I specialize in finding and analyzing deals, which I do, how can I partner with other people? Family members are not an option. Could I raise a small amount of money for the down payment and rehabs? Like a small syndication?  Thank you!