Not 100% relevant, though may be of use.
When researching the rental market - I went to www.booking.com
here you can advertise your property for rent & is very popular.
What I found useful is you can ascertain prices and even look at booking schedules online, so you can see at what price, how busy etc - so this will give you a more accurate idea on what you should be charging, as well as (importantly) how busy other similar properties are rentals wise. If it becomes apparent that on the booking site apartments in your location are much busier than your current bookings, then you either need to consider the use of a website similar to this - or a rental agent with more clients!
For anyone looking to buy a property for rental investment only - looking at something like www.booking.com
should give you an idea in advance of how long and for how much you can rent your property - before you go and buy something on the promise of an estate agent.
IE a genuine possibility of a reasonable calculation based on rental yield income of similar properties, in the same location.