There are two primary agencies that offer online certifications--the Institute of Real Estate Management (IREM) and the National Property Management Association (NPMA). Each offers courses such as site management, marketing strategies, financial tools, contract agreement and risk management. They are all instructor-led online classes.
The IREM offers three levels of certification--certified property manager (CPM), accredited residential manager (ARM) and accredited commercial manager (ACoM). The NPMA also offers three levels of accreditation--certified professional property specialist (CPPS), certified professional property administrator (CPPA) and certified professional property manager (CPPM).
Once you have reviewed the recommended reading and taken the certification courses online, you can then sign up to take an online exam. You must also apply for re-certification every five years if you go with the NPMA certification course, in addition to having participated in continuing education events.