The 10/10/10 rule is not a law, but a guideline.
Before you make an offer, it helps you construct an offer that will be profitable if accepted. My suggestion is that you offer AT LEAST 10% below the market, NO MORE THAN 10% down, and NOT MORE THAN 10% interest.
In my book I explain that most successful investors learn to finance properties without going to a bank. I have never borrowed from a bank to finance a purchase. If you borrow from a bank, you will need to make a larger down payment.
Today an investor with good credit and income can get an 80% conventional loan with an interest rate near 6%. Not everyone has the credit and income necessary to qualify for a “bank” loan. I see some paying more than 10% interest to hard money lenders to buy houses on which they hope to make a profit.
These buyers are often borrowing most or all of the entire purchase price, so they have to pay a risk premium to a lender willing to take a chance on them. I have made many of these loans in the past, but will not again. They are too risky for both the borrower and the lender.