Under which circumstances would I need to use a guarantor when applying for an apartment rental?

There are multiple situations where you would need to use a guarantor in order to get approved for an apartment.  These can include the following: not meeting minimum income requirements, possessing bad or no credit, having limited work history / recently starting a new job or not being a U.S. citizen.

Income Requirements
The standard annual income requirement for most management companies / landlords is generally around 40x monthly rent.  If you do not meet this requirement, you will most likely need to find a guarantor to include with your application, as a certain level of income is necessary for approval.

Bad or No Credit
If you have minimal/no credit history or possess a sub-par credit score (generally 700+ is considered optimal), this could reflect negatively on your application as mgmt cos / landlords consider credit a major factor when making their approval decision.

Limited Work History / New Job
If you have limited work history, are starting a new job or do not hold full-time employment, this may be an issue in the eyes of the mgmt co / landlord.  Showing present and past stability with employment is important and could impact the application process, if not shown in a positive way.

Non U.S. Citizen
Most non U.S. citizens do not have U.S. based credit history or a credit score, which is usually a good indicator of a tenant’s financial past and an essential determinant in the approval process.  As a result, international applicants can be immediately disqualified unless they include a guarantor with their application.