The extra $20 is just to cover the pool maintenance. The feature of having a pool is factored into the rent. For some areas you need a pool to attract a certain kind of tenant. In other areas not.
If you can get away without a pool then obviously less headache when something goes wrong. This...
I have an IP with a pool in the tropics. It is a pretty standard feature and desired with tenants of higher rent properties (my other lower end properties don't have pools).
We charge an extra $20 a week and include monthly pool maintenance. No issues so far but between tenants you should...