For example, Rentec is going to let you do online ACH payments with your tenants and provide them a portal to check their accounts, etc.

Then cashflow split would be transferred via ACH bank transfer as to have paper trail for tax purposes.

Everything is online, and I can accept ACH rent payments for only $.50 (yes, 50 cents). 

Meaning if you get the wrong tenant, and eventually you always will get 1 bad tenant for every property in the course that you own it, you're going to have head aches.

I would like to rent to medical students (Baylor College of Medicine), doctors, hospital employees, and Rice University students and not anyone else. 

There is currently a children's hospital, a VA medical center, several medicine-related colleges, a research center, and will have a teaching hospital eventually.It's just South East of the Orlando International Airport.

Also: we only take electronic payment on anything rented this way, one-way ACH.

If it is a prepaid debit card check have them check with the card issuer if the card allows ACH debits.  

The only rent payment site I've used took 4-5 days to deposit to my account.Do all online rent payment sites that 4 business days for ACH transfers to process?

I use an ACH service which debits the tenant's accounts.