How much of OPM should you use for downpayment?

[Jonas Törnqvist]

I've searched everywhere for this answer but I can't find it. I know that you get greater returns on your investment if you find a good deal and use OPM as down payment, but does this mean I should 100% use OPM or is it more like 50%?

Example 1:

$100 000 purchase price

$80,000 loan at 4% interest

$20,000 of your own money as down payment

Assume the total net income is: $2500

ROI then becomes 2500/20 000 = 12.5%

Example 2:

$100 000 purchase price

$80,000 loan at 4% interest

$20,000 down payment of which you borrow $10,000 from an investor at 7% interest

Total net income is: $2500 - (10,000 x 0.07) = $1800 

ROI then becomes 1800/10 000 = 18%

Example 3:

$100 000 purchase price

$80,000 loan at 4% interest

$20,000 down payment of which you borrow $19,999 from an investor at 7% interest

Total net income is: $2500 - (19,999 x 0.07) = $1100

ROI then becomes 1800/1 = 1800%

What should I conclude from this?

How much OPM should I use?