If paying PMI, you can always find a mortgage calculator and input your own figures to get an estimate for monthly payments after your escrow account. 

what is typical for a down payment if someone owner finances?

If I buy property A using conventional loan with 20% down payment, 5% of purchase price as closing cost estimate and $7K in repair, I'm looking at out of pocket cash of approximately $30K.

It would most likely trigger the due on sale clause.A scenario that may work though is if the amount remaining on their mortgage is less than what you are willing to offer as a down payment or they were willing to pony up the difference.

So the $700 payment on a home that rents for $1200 is still a decent cash flow.

Your results will be better, albeit more work.You could also create a holdings company for all your entities as I have done with various digital enterprises.

Down payment?

This is what the contract says about the Non-Refundable Down Payment;  The Non-Refundable Down Payment in the amount of 10% shall apply towards Buyers purchase price or closing cost.  

That way, sons pay for the down payment, make the payments, parents are the residents, and sons acquire ownership in the future.

Taxable Value 75,830Purchase 50,867Tax 1986.70Vacancy 10%Repairs 5%Capital Expenditures 5%Property Management Fee 10 %Investment results: Purchase Price: $50,867.00 Purchase Closing Costs: $3,000.00 Estimated Repairs: $0.00 Total Project Cost: $53,867.00 After Repair Value: $70,000.00 Down Payment: $10,173.40 Loan Amount: $40,694.00 Loan Points: $0.00 Loan Fees: Amortized Over: 30 years Loan Interest Rate: 5.000% Monthly P&I: $218.45 Total Cash Needed By Borrower: $13,173.00 Monthly Expenses: $643.95 Total Cash Needed: $13,173.00 Cash on Cash ROI: 5.11% Purchase Cap Rate: 6.48% Really, I know it’s not a great deal, but it’s a property that I can buy into for cheap.