Some of the ways you can earn 5K USD or more monthly online are:
Pay per click advertising
Affiliate marketing (only if you live in USA, UK, Canada, Australia), if you live in other countries, your affiliate commission may not be credited to your account.
Freelancing
Depending on the amount of automation used, the first two can be a passive source of income. However, freelancing is a service and you will be paid only as long as you work.