Q: Who is responsible for repairs to a rental unit?
A: This issue, as well, depends on the stipulated terms and the local practice of most people for such a dwelling (Rema 314:2; Aruch Hashulchan 314:1).
If the common practice is unclear, the guiding halachic principle is: Repairs that require professional service or that relate to the structure of the house for proper dwelling are the landlord’s responsibility; repairs that are not of a professional nature and relate to daily use are the tenant’s responsibility. 
For example, structural, electrical and plumbing issues necessary for proper maintenance of the house are the landlord’s responsibility; light fixtures, furniture and appliances are the tenant’s responsibility. If the tenant paid for repairs incumbent upon the landlord, he can deduct it from the rent (C.M. 314:1; Kesef Kodashim 314:1).
Affixing a mezuzah or roof railing, which are obligations upon the dweller, is also the tenant’s responsibility (C.M. 314:2; Y.D. 291:2. See Pischei Choshen, Sechirus 6:[6] regarding the railing of a porch intended for use).