Foreclosed Properties Not for Sale

[Rox P.]

I am looking at foreclosed properties for a small REI -small condo or small 2-3 flat for house hacking- in the Chicago area. I see that some appear as foreclosed for a while, over a year sometimes, and appear as owned by the Federal Hone Loan Corp or similar entity, but they are not being listed for sale at the moment. The message I see is as follows:

Foreclosed Home

We are sorry, this foreclosed home is currently not for sale.

It is owned by:

FEDERAL HOME LOAN MTG CORP

Can somebody explain how this works?  Why are they not available for sale?  What steps can I follow to make an offer in this type of property?