Showing Rental to Prospective Tenants as Out of Town Investor?

[Michael Giuffre]

I'm in the process of vetting an out of state market for rental property purchases with the intent of building up my "passive" net cash flow.  Since I live (Raleigh, NC) about 4 hours drive from the market I've honed in on (Baltimore, MD) I'm curious if other landlords out there have a good system in place to allow some sort of lockbox to allow prospective tenants entry to view the property.  

I was originally thinking of bypassing a property manager for tenant placement, and learn to manage the monthly operations on my own from afar, but I'm not coming up with any great ideas for how to ensure a safe, quick and successful prospective tenant viewing process from afar by myself.  Can anyone shed some light on if this is possible, or if I need to bite the bullet and pay a property manager their fee of 1 month rent for tenant placement services?  I'm happy to drive to the property and set it up with keys/lockbox but I'm not able to make multiple 4hr trips during the week to show it since I also work a full-time office job.  Thanks in advance for any and all advice.