It depends on what type of loan you get. For an FHA backed loan you would need 3.5% or $7,000. For a USDA loan (and dont let the name fool you, you'd be surprised how many areas qualify) you don't need any money for a down payment. And, for a conventional loan you need 20% or $40,000.
The best thing to do is talk to a local mortgage banker to discuss your options. Basically, once you get past the 3.5% mark it's what you have saved and are comfortable paying. You want to make sure you have a monthly payment you can afford also. So, you may want to make a bigger down payment to keep the monthly payment low. Or, you may find a home that needs a little upgrading and prefer to use the money to do the upgrades. It's really a matter of choice.