Should you create a selling account or webstore for your SA items that is separate from your main selling account?
If your designated SA account or store is new and doesn’t yet qualify for volume selling benefits like increased search exposure, it can mean lower sale prices for your clients’ items than you enjoy on the items listed in the main store. Just as when you sell through the client’s account, selling from a separate account means that your other items for sale won’t benefit from any cross exposure and your main account won’t reap the benefits from the sale of client items. Of course, your account also won’t get saddled with any negative selling experiences such as bad feedback or claims that result from client items. It also makes reporting that much easier when all your SA items are segregated into their own account and their fees are not mixed in with your other items. If a client’s items are a poor match for the items you usually sell in your main store, you may want to separate them out.
If you predominantly take on SA items that are similar to the items you usually sell for yourself, or if you sell such a wide variety of items that there’s nothing that wouldn’t really fit in your main store, you probably don’t need a new account. But it doesn’t need to be an either-or solution. I sell my SA items predominantly in my main storefront, but I do have alternate selling IDs that I use when the occasion arises.