Don is spot on as always. The amount of the downpayment will depend on the type of loan that you use.
VA and USDA (rural homes only) loans require 0 downpayment.
FHA requires 3.5% downpayment
Fannie Mae has a program called Homepath that can require as little as 3% downpayment.
Conventional loans will be 5-10% with insurance, 20% without.
Talking with a lender is the best path to finding the right loan for your particular needs.
I would team up with an experienced lender in your area... it will greatly help you with questions like this. There are a lot of different programs so the amount varies. The typical FHA purchase requires 3.5% and a conventional loan requires at least 5%. There are other programs like USDA that do offer 100% financing options so you may want to see what areas near by offer these programs as they are really helpful when trying to qualify a client with limited funds for a down payment.
I'm a Realtor and Mortgage Broker in the Austin area so if you ever want to chat about programs or real estate feel free to give me a call or shoot me an email.
REALTORÂ® | Mortgage Broker
Keller Williams Realty | 360 Lending Group