The guy I signed up with basically knew nothing more than me filling out the application. 

Full disclosure, I only deal in LTR at the moment, but I know when I am not getting the quality applicants or volume that I want, I will lower the price by $50 to $100 per week to spur more applications. 

.: The applicant needs a social security number or an individual tax ID number (ITIN).

If you have a few single family rental homes and are looking for a way to streamline leases, applications and rents, maybe rentredi is the right solution, but if you have a multi unit property or any serious management needs, look elsewhere. 

For example, I mention that every adult must pay a $30 application fee, pass my credit/criminal background, make a combined income of 3x the rent, and whether or not the property accepts pets.

They don't ask for any documents just do a credit check and you fill out their application.

Your comments are misguided, too specific to only one of your clients, not applicable to general investors and therefore not worth responding to. 

I know property managers in every state who use non-refundable application fees and it is the standard for every class of property and applicant.

Look at the application, start pricing third party flat fee services for each step.

Mortgage lenders will qualify you for a higher purchase amount for multis than they would on a single, because they will count the rent you will be making on the other units as additional qualifying income for your loan application.