Listed above was the opinion of one realtor who felt you shouldn't attempt to purchase a house if you did not have atleast 5% to put down. That is a somewhat biased opinion and should be taken with a grain of salt. While some realtors may know this subject with having worked with some borrowers in their pasts to help them through this subject matter - I'll give you an answer coming from a mortgage lender's point of view..
Unless you're trying to go for 100% financing, which comes in the form of government down payment assistance, either in a loan or a grant, you will most likely be looking at a few thousand down, no way around that. The days of the 100% financing, coming from one lender ended 7 years ago.
Now we're left with two distinct paths..
With The FHA loans, which are the more common first time buyer's loans, (insured by the gov't) are typically best suited for those under the 700 fico scores, haven't had a lengthy or perfect credit hisotry and those with a debt to income ratio that's over that 45% mark. These loans require the minimum 3.5% down.
Conversely, the Conventional loans, which usually cater to those with higher than a 700 fico score, and depending on the bank or lender, can sometime be more picky in your credit history, generally offer a lower over all payment month than the FHA (because of the cheaper mortgage insurance - another subject matter we can talk about) usually work with the atleast 5% down. But almost all of the conventional style loans are not eligible for the down payment assistance - atleast every institution I've researched. I could be wrong?
For down assistance programs, There is a CHFA loan, which works in conjuction to the FHA loan and covers that 3.5% down payment in the form of a second loan. These are subect to household income, counties you're looking in, and other minor factors. many times, if the sale and the loan is positioned most beneficially to the buyer, then I've seen first timers with a CHFA loan get there first home for around the $1000 program fee -and not money down. (seen other who put a little extra for a couple small things out of pocket)
AS Well there is the CHAC grant, which as mentioned in a comment above, is like the CHFA loan, can go up to $15k and is a grant you don't have to pay back. Again, certain income, credit criteria and other situational criteria apply.
As a mortgage banker myself, I'd be happy to talk to you in depth and provide you some more answers and estimates.
LEt me know!