So, what are your options?
1. Employ a web designer in-house
This is a good option, but how much does it cost to employ someone full-time? And what would the skill level of the person you could afford to employ?
2. Learn web design yourself
How long would it take you to learn enough web coding to be capable of this? How many times will you damage your website whilst learning?
3. Pay a maintainance company
This is the safest option, but again how often do you actually need their services? But you still have to pay a high monthly cost “just in case” you have any issues.