How do I setup SERVICES in ZOHO Books and ZOHO Inventory

How do I setup SERVICES in ZOHO Books and ZOHO Inventory

We have an Appliance business.

We offer many services that do not include physical items, but we need to add them to Sales Orders.
  For example:
   -We offer Curbside/Garage Delivery Service.
   -We offer Delivery & Installation Service.
   -We offer Repair Services.
   -We charge Trip Charges for clients outside of our normal coverage area......etc

We have been using ZOHO Books for the past 8 months.
In ZOHO Books, we made these Service related charges their own Item, and labeled the Unit as Labor Services
Unfortunately, I don't think we did it correctly, because we ended up with (negative) Qty for each of these Items because there was never any stock-on-hand to begin with. They are services, not physical products

Now that we have added ZOHO Inventory to help manage our Inventory levels, and process transactions more properly through the entire lifecycle of the sale, we are experiencing some problems.

1. When I create a Sales Order, if an Item has  negative Qty-On-Hand, it produces an error message saying invalid_item_id or something like that.

So I went into the item, and modified the Qty on Hand to be a positive number. That fixed it, and let me process.

However, we Drop-Ship many items that are not in stock. Is ZOHO Inventory not going to let me enter those items because they are not a positive Qty On Hand?

Please Help.
Thank you,
Ben