Best Down Payment Method

[KJ D'Costa]

Our long term strategy is to buy and hold multiple four-plexes. And 20-25% down seems to be the standard down payment required to buy a 1-4 unit property. Our thoughts are to rehab/flip homes to accumulate the funds needed for the down payments, as we don't want to touch our current capital (about 75k). 

Is there some other financing method that I'm not aware of?  I want to make sure I've uncovered all the possibilities, before we put our energies into rehabs?

Thanks for any guidance. (We're in Central Texas, btw).