Here is a secret from my business:  I don't meet with potential clients unless I first have an idea of their budget.  I don't need a spreadsheet with every penny accounted for (In fact, I really don't want that!) but I do need a starting number that they feel comfortable with.  

Here is another secret to getting this number: You ask.  Then if they don't know (many don't and this is okay!) then prob further.  Keep asking in different ways to get a number from them.  Don't waste their time or your own entertaining a project that is an impossible budget.  Usually there are two types of clients, those that have a number but don't want to share it because their afraid you'll abuse their money.  Or they really have no idea what it should cost.  If you're lucky you'll get a client that has an appropriate budget.  If you're unlucky you could get a client that has an unreasonable budget.