There is no set amount of money or particular percentage of the purchase price of a property that is "required" as a down payment for you to proceed with a purchase transaction. A competent mortgage lender can speak with you about your specific loan and overall financial needs to suggest a loan product that might work best for your situation.
If you'd like a list of mortgage lenders that I've successfully worked with in the past, I'd be happy to provide you with some names.
After having contacted a lender, if you are planning to use a real estate agent to assist you with your transaction I'd be happy to help you.
Good luck, and let me know if you have any additional questions.
Broker Associate, Sudler Sotheby's International Realty