Will you be around to help us after making the website?
It makes us really sad every time we hear stories of freelancers who build a website for a business, then become really difficult to get in touch with afterwards, or disappear altogether. There are many reasons they might do this, but none really excuse this behaviour.
Rather than trying to ensure this never happens, the best thing to do is ensure it isn't a problem for you by looking at the alternatives.
Firstly, make sure that your site is built in a way that isn't too unique and specific to the person or agency that built it. For example, make sure that it's built using popular software like Drupal or WordPress, and make sure the developers haven't included too much custom code that other developers won't be familiar with. How? Just ask them to explain how they plan to build your site, and what parts they're developing instead of sourcing from the wider community.
If you need support for your website, there's a pretty good chance it's built in a way that we're familiar with, so get in touch to chat about it.