Office cleaning in New York is bought by the building as often as by the tenant. A property manager may ask every vendor for a certificate of insurance that names the owner.
A tower may book the freight elevator for set hours, so crews work at night and use the service entrance. Some buildings have existing cleaners or approved vendor lists, and some tenants hire separately for their own floor.
So your first sale is often a question: who decides here? Midtown towers, converted buildings in Downtown Brooklyn, medical suites in Queens and retail strips across the boroughs each work differently.
New York State has no janitorial license, so buyers look for proof elsewhere: insurance, workers' compensation, background checks and references you can share.