You see when you need to go beyond what came out of the box, you’re suppose to create a custom theme folder where you’ll house all of your modifications. This is not restricted to theme overrides but also plugin overrides using your child theme’s functions.php file.
When you do this, all of your custom “overrides” are contained in the folder that you created which is not going to be upgraded when WordPress prompts you to do an update.
That’s how it’s suppose to be done so that you aren’t stuck on an obsolete version inheriting more and more security threats as it becomes more and more obsolete.
Last but not least, if you’re forced to run an obsolete version of WordPress, you don’t benefit from all the new features that get released every day and are often free.
What will it cost?
If your WordPress website wasn’t customized with any php modifications (custom programming/code) it should be straight forward and cost no more than $100…
If a plugin you are using has been discontinued and is no longer supported, we may need to write some custom code for you unless we can find a new plugin to replace the old one.
That said, if you have already tried upgrading but the website broke… it really all depends on how much was customized by your previous developer.
Furthermore, if the previous developer did not leave any notes for the next developer, we’re going to need to reverse engineer the whole thing which takes more time.
To save on costs, the best thing you can do is get a list of all the customizations along with the location of the files that were modified from your previous developer.
If that’s not possible, then perhaps make a list of all the changes you requested in the beginning as they will likely need to be done again.
Is there a warranty?
The only warranty we make is that things won’t get worst. In such an event, we are prepared to restore the site as it was before we started and give you your money back. That’s right, if we can’t fix it, you get your money back.