I am not a lender's representative, so it may be best to actually contact a qualified lender or lender's representative in your area.
However, the first step is to determine value, which often is the price that is being paid, (if the price is not discounted by the lender). The lender will either do an appraisal, or apply comparable sales data, to the subject property. The financial institution will certainly consider the income generated; and the expenses used to maintain the property (NOI) to find a debt service coverage ratio as well. This ratio is found by dividing Net Operating Income from the property, by Total Debt Required in financing.
However, to stick with the question you asked the second step is to determine what a specific lender is going to require with regard to LTV (Loan to Value).
For simplicity, if the value of the property is determined to be $600,000 and your loan is $450,000, your loan to value is 450,000/600,000 = 75% LTV.
Thus, the amount of the loan divided by the established value = LTV.
There are many LTV calculators available by searching on the Net for "Loan to Value Ratio".
Onward and Upward....
CA DRE #544165 (one of the oldest active licenses in the State)
AZ DRE #BR 641305000
Mar 12, 2013