My partner and I put in equity 50/50 and got hard money financing in the beginning to put less down, and then we either refinanced or 1031 exchanged into larger assets.

It does seem that rates are going down, and at some point like you say we will end up refinancing to a perhaps somewhat larger rate on a 1st position mortgage to consolidate.  

I see people owning much larger housing space and paying more for heating, cooling, insurance!!

Larger, more unique do better. 

The single family renovation is financed by a different lender than the larger development parcels.

Staggered balloon payments allows you to plan in advance what years would have the larger gains.

I’m looking at a similar strategy as you, starting with a small investment first — but I’m eyeing a larger investment in the future for sure. 

With many buildings the larger the unit and the higher the floor the higher the taxes.

Perform the same task in each app to ensure a fair comparison.Load a property with pictures and details.Market that property.See what your marketing looks like from the public's perspective.Submit a fake application to see how easy the process is.Run a credit/screening report on yourself.Enter a maintenance request, assign a vendor, and attach a fake invoice.Enter charges to the tenant's ledger.Enter recurring charges and automatic late fees.Sign documents electronically.Run owner reports.After testing a few apps, one should clearly stand out.

As you grow larger it will be impossible to meet even a fraction of your tenant population.