What actually constitues a Florida mortgage being in default to the point that foreclosure proceedings begin? Is there a set amount of months one must be behind on their mortgage before the lender can begin foreclosure? I heard if a borrower is 3 full months behind & going into the 4th month, then foreclosure proceedings can begin. Is that time frame a standard guideline or does the time frame need to be spelled out individually for each mortgage?

That is generally up to the lender though there may be some guidelines in state law. Check with the state banking agency.

This may be of assistance:

Florida Foreclosure Law