I would recommend everyone to manage their own property on the basis it is impossible to do any worse than the "little girls" at your local RE Agency who are poorly trained, underpaid and not equipped for the job.
But is is like any job, if it's worth doing do it well.
Most property managers should be ashamed to accept their commissions.
You don't have to keep your rents low, charge the market price, but as in any business you have to give service. If you had a valuable race horse would you keep it in a wet paddock with no feed? because if you did your income would drop. Its a bit like painting a house it's all in the preparation, get the basics right and then it is soooo easy Look after your property and treat it as the business that it is, most people fall down because they have never had the experience of running a business.