And determine how the payment and approval for work will be take care of before hand. 

You can take advantage of lower down payments but you just have to make sure of your numbers.

Private money - $10,000 down - my private money lender said I didn't have to put any money down but I wanted to keep the payments at a certain amount for cash flow.

Secondarily, even if you feel you have a viable claim it's important to understand who will be responsible for payment in the event you succeed.

I wonder if anyone used Venmo to collect rent payment?

The buyer is always responsible for that payment, but is relieved when the seller provides the incentive that will pay that fee for them.

Bought my primary residence in 2019 and been practicing the BRRRR method (more or less, currently in the process of turning it into a short term rental here in the Santa Cruz, CA area.

Since starting my wife and I have yet to miss a single payment of rent, we have batted 1000 for over a decade (just made youtube video on it that goes into greater detail) but the main reason behind it is because we avoid areas that are extremely tough for landlords. 

I was told in writing before signing the contract that the tenants were current with payments and were paying $2,000 a month on time every month. 

If there were payment issues with the original subs, this becomes even trickier and could result in clouded title with mechanics liens.