When will your items be ready to ship? Keeping Inventory vs Build to Order
There is no right or wrong way to handle inventory. It really depends on your customers and your products. If the majority of your customers choose custom options you may build everything to order and decide not to keep an inventory at all. If you sell larger volumes or simpler items and you produce them in batches; you will be keeping a certain number of items in stock that are ready to ship at any moment. If you do build to order there are a few points to consider.
Be sure to make it very obvious to any potential buyer that the shipping will not be immediate. Use larger font, bold text, or put it into the title of your item. Also put it into the description. Make sure that they know the time frame of when they can expect their item to ship.
It is a good idea to send your customer a nice email after the sale thanking them for their order and again mentioning that it will be X amount of time before their item ships. You cannot be certain that your customer read your description. For longer build times of multiple weeks you may also want to send your customer updates or even progress photos.
There will be times when a customer is in a rush and will ask if you do have anything in inventory that can be shipped out right away. If you receive questions like this on a regular basis you can mention more prominently on your website that all pieces are built to order and that you do not keep an inventory. Another way to look at it is you may want to keep an example of each of your most popular items on hand for customers like this. That would keep you from losing customers.