If you have me develop your site on a Content Management System, I recommend WordPress using the Avada theme. Millions of developers all over the world use this theme because of its flexibility and many built-in features.
I offer clients training if they want to maintain it themselves. You don’t have to be a techie to do certain things but it would be good to be comfortable on a computer. Training is best in short spurts so not to overwhelm and then forget half of it.
Rule of thumb with maintenance on a site is you can do the simpler things (eg, adding a blog post, editing typos, adding images to the simpler slideshows). You could add pages but there are several more steps for this. If you are a good note-taker then this could be doable. The much harder parts, you should leave to the developer/designer. You might want do it to save money but if you mess it up, then it could cost a lot more for me to fix the problems.
I can maintain sites that aren’t on a Content Management System (HTML only), but it will most likely take longer to do the work since I would have to study the way the site was programmed and it may not be expertly done. I would not recommend you maintaining an HTML only site it yourself.
If you wish me to do updates and edits for you, the costs depend on how frequently (such as: every month or week) and how much needs to be edited. If you envision regular updates, you could buy bulk hours from me which may be less per hour than as needed.