The more money you put down;
The more Equity you will have,
The easier it will be to get the Loan,
The Interest Rate will be lower,
Your monthly payments will be lower.
Backing up from August, I would say May/June to start talking to a Mortgage Officer.
I would also suggest something like Garage Saleing in the areas you might be interested; this gives you something to do while you are looking, and talking to people.
I can e-mail you possibles, but you want to know the neighborhoods yourself.
Good luck and may God bless