immediately post the property for unlawful detainer and start the  paperwork.

Once the 3 days have passed and rent has not been paid, then an unlawful detainer claim is filed in court.

If they are the senior lien holder, they will more than likely bid total debt and take it back into REO, rehab it (Maybe), evict tenants, and sell it on the open market by listing it with an agent.It's a simple unlawful detainer (eviction).

I doubt you will have to provide a reason given he is on a month to month tenancy but you should get it cleared with an Ohio attorney so as to not have the judge kick your unlawful detainer for improper notice.

Your unlawful detainer claim should have included all expenses allowable.

You can (and should) start your unlawful detainer action immediately with a competent attorney that specializes in evictions.

Then go to the local magistrate court and file an unlawful detainer lawsuit.

If your tenant is now a squatter then an unlawful detainer may be the appropriate filing in your state.

Spend some time eduction yourself on  how unlawful detainers work in your local market. 

@Horacio Gutierrez  In California, after the 3 Day Pay or Quit Notice, if the tenant doesn't pay you can proceed right to filing for eviction (Unlawful Detainer).