Following are tools readily available on the web. For a small business, it’s a low cost way to have valuable tools for your business. The only cost involved would be the cost for support and any customization you need for your business. If you know how to install scripts and use the scripts barebones then it’s pretty much free.
ERPnext is an ERP platform you can use on the cloud or locally. It is open source, meaning, the underlying code is available for scrutiny and/or modifying. We are currently reviewing ERPnext for a customer. More will be added as time progresses.