If you don't meet a landlord's financial or employment requirements, you'll need to find a guarantor. A guarantor signs a contract that makes them liable if you default on your lease; for this reason, guarantors are usually close family members.
Most landlords will only accept guarantors that live in the Tri-state area (New York, New Jersey or Connecticut) and who have an annual income of 80 times or more than the monthly rent of the apartment you’re applying for. Typically, your guarantor will need to submit the same documents requested of you by the landlord (e.g. bank statements, tax returns, etc.). And if you have roommates, most landlords will only accept one guarantor--so that person needs to be comfortable guaranteeing the entire lease.
If you don’t qualify on your own and you don’t have a guarantor, you may be able to negotiate with the landlord to pay additional rent up front or a larger security deposit. Expect that they will ask for many months (e.g. 6), so this will require a substantial amount of savings to cover.
Alternatively, you may be able to use a guarantor service like Insurent instead. Its income and employment requirements are significantly less strict than a landlord's, though you'll still need to have a clean credit record. Insurent will guarantee your lease at an average cost of about 80% percent of a month’s rent if you have U.S. credit and 110% if you are foreign with no U.S. credit.