Subleases, Subtenants and Roomers (https://www.peoples-law.org/subleases-subtenants-and-roomers)
A sublease exists where the tenant leases all or part of the premises to another person for a period less than his or her lease term. Absent some specific restriction in the lease, the tenant has the right to freely sublet the premises without obtaining the permission of the landlord. However, the landlord may impose restrictions on the right to sublet the premises if stated explicitly in the lease with the original tenant at the time the tenant signs the lease.
Subletting restrictions may be considered waived if the landlord allows the sublease or doesn’t say anything about it. For example, a provision in a lease that the tenant may not sublet the premises without the written consent of the landlord is not violated where the lessee sublets the premises with the knowledge and consent of the landlord . If the lease provides that the tenant must obtain the landlord's consent in order to sublease, consent may not be unreasonably withheld. Reasonable objections to a prospective subtenant might include concern about his ability to pay the rent, or concern about his intention to use the premises for unsuitable purposes (Julian v. Christopher, 320 Md. 1 (1990) Overruled by Waller v. Maryland National Bank, 95 Md. App. 1976 (1993)).
In any sublease, the original tenant is still responsible for complying with the terms of his lease with the landlord and the subtenant is responsible for complying with the terms of his sublease with the tenant (Italian Fisherman, Inc. v. Middlemas, 313 Md. 156 (1988); Adreon v. Hawkins, 4 H. & J. 319 (1818)). The relationship between the subtenant and the landlord depends upon the terms of the sublease but a subtenant is responsible for knowing and, in most cases, complying with the provisions of the original lease (Glenn v. State Roads Comm’n of State Hwy. Admin., 33 Md. App. 476 (1976)).
A “roomer” is defined by the Code of Maryland Regulations as an individual to whom a household furnishes lodging, but not meals, in exchange for compensation. A relative who is 60 or older or disabled may also be considered a roomer. Read the Regulation: Code of Maryland Regulations 07.03.21.02 (http://www.dsd.state.md.us/comar/comarhtml/07/07.03.21.02.htm)
Generally, a roomer is not in a landlord-tenant relationship with the person who is renting the room to him, meaning that the roomer does not have the right to exclusive possession of his room and the proprietor retains general dominion or control over the premises.
Local laws and zoning codes may provide additional protections and/or regulations regarding roomers and rooming houses.
The following sources should be in your local circuit court or other public law library.
14 Maryland Legal Encyclopedia, Landlord and Tenant, Section 41
Douglas M. Bregman, Maryland Landlord-Tenant Law : Practice and Procedure, Sections 2-201 and 2-202 (4th ed. 2009)