How to manage the return after a rental

Do you mean “rent” them? Or it is just “in bail”?

I would use a return shipment. This way you can have the two steps “received” and “done” which is “incoming moves” and “inventory moves”.

Also I would use product of type “asset” so they do not generate any stock accounting.

And if it is really a rental business, you may have a look at the sale_subscription module and Asset subscribed. Your case may require to extend the last one to manage outgoing shipment and return at the start and end date of the subscription.