After recently speaking to loan professionals I have become aware of the fact that after you have a couple of properties lenders will require that you have 3-6 months of reserves for your loan payments for each properties on hand. 

My MTR is suited for travel medical professionals and digital nomads so I market it only on Furnished Finder.

How did you come up with the down payment with each property?

For primary residences, lenders typically don't require PITI (Principal, Interest, Taxes, and Insurance) reserves beyond the down payment and closing costs.

I think I have most of the kinks worked out but I'm looking for software (preferably free or very cheap) to digitalize the payments and bookkeeping from the house members.

Surprisingly, Craigslist yielded the best results as I found my first tenant whom has renewed twice already and has never been late or missed any payments.

And is there any path to a lower down payment using creative financing, or is 20% pretty much what it is? 

My tenant left without making a payment and upon inspecting the house I found a few damages to the property (like 3 doors need to be replaced ...etc).

If your looking at a SFR property, have good credit, and 5% down payment instead of 3.5% you may be able to get a better deal with a conventional loan. 

For example, if I take the DSCR loan myself and use a HELOC for the down payment, the property is in my name, but I have friends and associates who might want to invest, say $5k or $10k.