Are you (or just one person) going to be the only one running the app? Or will the inventory show up on some website or other mobile devices? Are customers going to buy items that will reduce inventory and will someone be adding items back? Will people be conducting sales from the app?
Certainly, Corona can act as a front-end to a server-based implementation, but I’m not sure you know the scope of this project. Point of Sale terminals are typically going to need to interact with a credit card reader. Many of those communicate through the headphone port, which Corona doesn’t support in the simulator. You might be able to use Corona Native builds to access native code that can read card scanners.
An inventory system requires very strong database knowledge. Setting up tables and relations between them will be a large part of the projects. If you plan to have this share on a server, you’re going to need to develop server based API’s using a language like PHP or similar hosting. That’s going to require a different set of programming skills. Corona, of course, can talk to many server-based APIs with the network.request() API call.
And of course, there is a lot to just build the device side of an inventory/POS app. This is by no means a small project.
Rob