1. Who are you going to get for a 24 hr emergency maintenance person?
2. Who is going to check on the unit to make sure it was really cleaned and laundered after every booking?
3. Are you willing to take phone calls and spend the money on self booking sites like http://www.homewaway.com and http://www.rentalo.com?
4. Are you prepared to go through all of the legal procedures to get your property up to code and licensed to rent?
management companies take care of all this and more and while I am not their biggest cheerleader I definitely find them to be necessary if you live more than a few hours away. Also read my article on the 10 questions to ask any management company before you hire them. It will guide you on how to avoid hidden fees and such.
Good luck with your STR investment and remember, if I doesn't have a pool it doesn't get bookings!!
"The Flamingo Has Landed"