Is it a big job to upgrade a script from 5.6 to working on 7.4 PHP?

Is it a big job to upgrade a script from 5.6 to working on 7.4 PHP? I have a few script I made some money with but I am not sure how hard it is to hire someone and upgrade the PHP and if it is even possible?

I'm afraid it all depends what was in those scripts. If they were very simple, then I shouldn't be a big deal. You may look at this link https://www.php.net/manual/en/appendices.php at "Backward incompatible changes" links and try to compare if any of mentioned incompatibilities exists in your project. Especially look at https://www.php.net/manual/en/migration70.incompatible.php because probably that will be the biggest pain, if any.

Ok thank you the script is not complicated it just a huge database