Very different answers to your question depending on the answer to this one.If for a career path, I would agree with @Michael K Gallagher and find a brokerage that is actively doing deals, has a property management division in house, and has brokers covering each of the key market segments - multi-family, retail, office, industrial and land.

Like with other tenants, screening is key. 

For those who’ve used private money for multiple flips, how has it impacted your ability to scale? Are there any pitfalls you’ve encountered? Let’s talk strategies and lessons learned!

Proximity is key.  

Just like any other relationship, communication is key. 

This creates two loan payments ($100,000 of equity and $300,000 on the new mortgage).Key NumbersHome Equity Loan Interest Rate: 6%Mortgage Interest Rate: 7%Rental Income: $3,000 per monthExpenses (management, taxes, insurance, maintenance): $800 per monthIncome and ExpensesMonthly Rental Income: $3,000Monthly Expenses: $800Monthly Mortgage Payment: $2,000ExplanationThe investor earns $3,000 in rent each month.They pay $2,000 on the investment property mortgage and $800 on other expenses.This leaves $200 profit each month or $2,400 per year.However, you have to pay $6,000 interest on the equity borrowed.This leaves you with an annual loss of $3,600.This example shows that while the rental property generates positive monthly income, the interest cost of borrowing the initial $100,000 results in an overall annual loss.

Aside from some answers below, location is key.

For me the 'key' was finding a mentor willing to push me and help me figure out what, when and how to do it.

Owner has 180 days to redeem and my purchase price would be paid back if he does so.I see two key risks I am worried about:1) Owner stops paying the mortgage and bank initiates foreclosure. 

Being able to bring verification of ownership from the seller is key.