Md. Code, Business Regulation § 15–205

(a) For an individual who is under the age of 18 years, an innkeeper may require a parent or guardian of the individual to:

(1) accept liability for the charges for the individual’s lodging and any damages to the lodging establishment caused by the individual; and

(2) provide a valid credit card or make an advance cash damage deposit of not more than $500 to cover any charges incurred or damages caused by the individual.

(b) If an innkeeper requires an advance deposit under subsection (a) of this section, the innkeeper shall, following a room inspection at the time of checkout, refund any amount of the deposit not needed to cover reasonable charges for damages.