Is accepting ONLY electronic rent payment illegal/discrimination?

[Mike R.]

curious if we included as part of our tenant eligibility requirements that any payments (late fees, rent, utilities, etc) made to landlord MUST be in electronic form (i.e. wired) considered discriminatory or illegal?  I haven't seen anything that suggests it is illegal/discriminatory but i have had prospective tenants claim they cannot make electronic payments (some credit unions have issues with electronic payments) and these prospects are usually in the lower income brackets.  I know, talk to a lawyer...but curious what other landlords think/have encountered.  

Personally, i don't believe the practice is illegal/discriminatory but you never know in today's anti-small business world.....

thank you for your time.