We’ve now been hired a several times to take over support of WordPress sites originally deployed by someone else. In two cases sites were set up using premium themes (i.e. paid themes) which were registered in the names of the developers rather than the clients. In one case this was a “favor” done for a non-profit outfit; in another a design company was paid by the client to create a WordPress site and the individual responsible had left the company. When the themes needed updating, neither client had access to the accounts where their themes had been purchased. With access, they would have been able to update their themes as needed, for free. Lacking access, they had to buy new copies of the themes. (After wasting a lot of time struggling to track down the original developers!)
In an earlier post I wrote about keeping control of your domain. Similar advice applies here: if you hire someone to set up a WordPress site and opt to use a pre-built premium theme, make sure to handle the purchase and registration yourself! The theme can be downloaded to your desktop and emailed/drop-boxed to your developer.
Although, as in the case of the non-profit, people typically mean well when they handle the purchases, in the end that won’t serve you well!