When you decide to buy a property to rent out to tenants you are taking on certain responsibilities. The day-to-day actions required from you may be less should you choose to hire a property manager or a company to help you with this, but in the end if you own the property, the responsibility for that property falls on you.
If you're acting as both landlord and manager of the property you may have quite a bit of work on your calendar (and certainly some that shows up suddenly). Tenants may call with complaints of noise, maintenance requests, or various other issues and it falls directly on your shoulders to fix it. You should always act in a timely manner to make sure that the tenant is taken care of to the full extent of the contract between you both. This will help to ensure a healthy relationship between you. While you should have certain policies in place on office hours and the like, you'll need to make yourself available during reasonable hours as well as if there's an emergency. It may be an inconvenience to get a call at 3AM, but if it's for a busted pipe that's flooding the rental home, both you and the tenant will benefit from a timely response.
Choosing to hire a property manager is decision that should be weighed carefully. It will depend on how hands-on you'd like to be with the property, if you have the time to take those maintenance and complaint calls, and how close you live to the rental. Keep in mind that even if you hire a manager, you are ultimately responsible for what happens. While the incentive should always be in favor of bringing in quality tenants, maintaining the property, and abiding by the landlord-tenant laws, if the manager doesn't do this it will fall on you. Poor tenant will cost you rent, damage done to the property will, ultimately, come from your pocket, and if your manager breaks the law you can be held responsible with them. As the owner, everything can come back on you, so you'll need to be very careful in choosing a manager. Make sure you can trust them and that they come highly recommended.
Owning a rental property can be a great investment, but it comes with responsibilities attached. Make sure you live up to yours and take care of your tenants and you'll be on your way to growing your business and investments.