As the others advise, you shouldn't need that much of a down payment.
You don't indicate whether you're asking about a specific property on the market, or just in general. For a specific property on the market, follow the advice below and your down payment should be far less.
If you're talking in general about buying a house (even an expensive house), there are dozens of creative ways to buy a house with very little money out of pocket. These range from lease-options and subject tos to equity sharing and owner financing.
In any case, though, talk to a good mortgage broker. Find out what you can afford, and what programs are out there. That's your first step.