It would depend on your bank and how far behind you are in payments. Usually, they will file for foreclosure within 3 to 6 months of not paying. You could be out of the home in as little as 6 months to as long as 18 months.
If you are already to the stage of them actually foreclosing on the property, you could get a notice from the sherrif anyday and only have 3 days to vacate.
Did you just stop or recently stop making payments? You should contact a Realtor who knows how to do short sales and offer your house on the market with bank approval.