In general the economies of scale as associated with the larger properties just makes them easier to manage and causes them to cash flow better.

In my experience, most people are better off just trying to sell their portfolio and buy a larger asset.

I don't personally have tens of thousands in cash on hand for larger down payments (I do though in my TSP/401k), but my dad will have maybe a couple hundred thousand after the sale of his house soon.

I would like to be prepared for a larger multifamily project. 

One thought would be for you to move into the smaller unit and rent out the larger unit to bring in more revenue.

From November 22 to December 29, step into a dazzling winter wonderland featuring twinkling lights, stunning larger-than-life sculptures, an ice-skating trail, and visits with Santa.

Or find a property that is under-utilized or has below market rents.Otherwise, you could also do the OPPOSITE of the great advice from @Jonathan Greene and buy a property with multi-bed units or live in the larger unit and rent out the smaller unit - while getting a roommate(s).

Larger Multifamily is currently a very overcrowded field as there are many multifamily trainers out there teaching armies of people how to buy it, who are all competing for the same deals, and sellers know it.

Plus the way these larger parties go through TP . . . .

I don't do large rent increases (like $200) because I don't want a unit turn but my rent is in the market range.