Not understanding the question well. I see that everyone else has replied according to their interpretation...
If you are asking how long is the process of foreclosure, then you got the answer from Meg, BUT, a property that is in the process of being foreclosed is not owned by the Bank (technically).
If the Bank already foreclosed, the property is owned by the Bank, so you could also be asking how long will it take for the Bank to take possession, get rid of the occupants.
I can also guess you may be asking how long does it take to close/purchase a property that has been foreclosed...if you clarify, I can provide a better answer for you, I do specialize on foreclosed properties and pretty much familiar with the entire process.