I am a landlord as well ~ scary thought. My rental property is also a block away, so I have great access for repairs or any concerns.
One site that helped me alot was
www.mrlandlord.com. There are alot of free forms on the site, and great advice from experienced landlords. I put a great lease together with the help I found there.
I am not aware of the percentages that real estate companies charge, but it can be a wise idea to let another professional handle the place in your absence. This is very common in beach tourist areas, for example, where the owners may live states away. If you can bring in enough rent to cover those costs and your mortgage, I think it's a great way to go.
You can also deduct any condo fees, and expenses involved when the house/apartment is not occupied. (when you are attempting to rent it out...)