The first question that pops in my mind is why do you have to split it equally? I'd encourage to list the room(s) for market value and pocket the profit. I would encourage you to include a flat rate for utilities in with the rent amount but average it out so that you'll be covered and not coming out of pocket. Just be sure to let the tenants know what they're paying for.
I wouldn't cut anyone a deal for renting both rooms unless you are in a bind and the area is hard to rent. Based on your intro, it sounds like the area is a "desirable location" so I assume that means it's desirable for one-room tenant renters as well.
I would do the math so that you at a minimum include the base rent (split 4 ways) just to make sure it's fair then I would bump up the base rent to market value plus utilities.
BP has lease agreement templates; we've used Zillow to list our rentals mainly because the tenants can do the apps and background through Zillow at their cost. Even if you list your room other places, you can still list it on Zillow just to take advantage of the app process. I'm sure there may are likely other tools for this but this is the one we've used.