When can I file a foreclosure proceeding to start the process of acquiring title?

Generally, six months after the sale date. However, in Baltimore City, if the property is cited by the city as vacant and abandoned, the tax sale purchaser can start the process and file two months after the sale!!!

What Delinquent charges qualify a property for a Tax Certificate Sale?

The liens include but are not limited to Real Estate Taxes, Special Benefits, Special Tax District, Alley Paving Bills, Footway, and Streetscape, Minor Privilege, Multi-Family Dwelling, Clean and Board, Water, Environmental Control, Residential Registration etc.