As several agents have suggested below,
Has most of the information you need. You do NOT need a permit to rent out your house in Frederick, MD.
I would also call the local courthouse and/or local association of Realtors. This would be the Frederick City Courthouse off of West Patrick St and FCAR (Frederick County Association of Realtors) of off route 85. Doesn't hurt to call a local brokerage or agent too for more information.
All the best,