Additionally, since the aforementioned demographics on property owners and management companies is accurate, you should consider alternative tactics.

What about modifying the initial workflow from the Tenants perspective and allow Tenants to make rent payments to Landloards who are not yet even on this site?

Seems like the easiest way to address your potential market (landlords) since there is certainly a huge demographic of renters who would like to use this service from the payment perspective. Changing the focus on the landing page to be directed at the Tenant -- as in PAY YOUR RENT NOW, and focusing on the benefits to the tenant as part of your conversion process.