Where do you find details on prices, demand, cash flow etc? 

.$300k cash flow in 20 years is an ambitious but not unrealistic goal. 

Long term rental numbers are hard to get cash flow with added in reserves for maintenance, cap ex, and vacancy.

How do others manage to create positive cash flow from MF properties with debt?

Leverage your existing equity to invest in smaller properties, such as a mixed-use or retail space, to gain experience and cash flow.

In short, the previous owner made a deal and sold the house while they were still living for monthly cash payments until they died.  

It’s a great way to grow faster.HELOC or Equity Tapping: If you have equity in another property, using a HELOC or cash-out refinance could help cover the down payment without affecting your DTI as much.Seller Financing or Creative Deals: Look for sellers willing to finance directly, which bypasses traditional mortgage qualification hurdles.Scaling quickly often involves combining strategies—play around with what works best for your goals.

Real estate requires cash, that's why it's called in-vesting.

I am a local agent here in Sacramento & I am a house hacker myself with 2 properties here that now cash flow.

While your partner accepts more of the cash from the sale of the FFE and the associated tax bill.This might take some accountant massaging.