@Kalos Bonasia - You could collaborate with your client on their boards as a guest editor - have a look at this help center article on how your client could set this up for you and do not the section that lists 'what guest editors can't do'. The board can even have a password added to it for extra security.

You could try this approach and if you find it isn't working you could request that your client purchases a license for you to join his paid Miro team.

@Robert Johnson  thanks for the answer and explanation. so it doesn't work like on google, where i pay my license and the customer his license and then we can work together. My client has to buy a new license for me and I would have two Miro accounts at this point. We hope that in the future you can think of a solution that who pays for his license can work by hooking up with others. I think it could be more convenient for everyone.

@Kalos Bonasia

so it doesn't work like on google, where i pay my license and the customer his license and then we can work together.

Correct - you can’t work together as two independent Miro license holders in one Miro team. 

 If you do go the guest editor route, one tip I have is that once you are in the board to which a link has been shared with you, click on the star icon beside the board name. Once you do this, you can easily find the board again from Miro dashboard by clicking on Starred boards - it’s a handy way to ‘bookmark’ the board from right inside of your Miro account rather than saving the board in your browser bookmarks, an email, etc. Just note that as soon as the board owner sets Anyone with the link to No access, it will of course disappear from your Starred boards page.