You should always try to find software on the market that will suit your need before writing your own.

Ready-made software (open source or commercial) has quite a few pros included:

Updates
Support
Maintenance

Writing your own software is a long term commitment and if you are not in the software business or you are not planning to be in the software business in most cases you would not be able to deliver and maintain good quality software.

That said there are lots of cases that you will need some sort of integration or customization that would not be achievable by using a proprietary solution.

There are many fiverr clones and Wordpress themes available online, you shall evaluate all before making a purchase.

I've successfully helped over 150 entrepreneurs, startups, and businesses, and I would be happy to help you. Please send me more information before scheduling a call - so I can give you maximum value for your money. Take a look at the great reviews I’ve received: https://clarity.fm/ripul.chhabra