SharePoint Foundation 2010 is free of cost if you don’t count the software and hardware needed to run a server. It offers the same basic functionality as SharePoint Server 2010 while SharePoint Server 2010 extends it with regards to the standard or enterprise license.
If you need to install SharePoint Foundation 2010 you can use the same steps as you would use to install SharePoint Server 2010.
See here for a detailed list of steps: Install SharePoint
The SharePoint Foundation 2010 software and hardware requirements are the same for Foundation and Server independent of the environment and component… you need the same things for the database server in a farm, a single server with built-in database or Front-end Web servers and application servers in a farm.
You need the same hotfixes and patch level for Windows Server 2008 as well as SQL Server. Also the roles and role services which are activated on Windows Server 2008 are the same compared to SharePoint Server 2010.
The steps during the installation process cover the same things: For a development environment you need Windows Server (2008) as the operating system for the server where SQL Server and SharePoint 2010 will be installed. Additionally you need a server for the installation and configuration of Active Directory.
After you created the servers with the basic installation you need to enable roles and role services. In your Active Directory you will create domain accounts used to install and configure SQL Server and SharePoint 2010. After the installation of SQL Server you can deploy SharePoint Foundation 2010.
Differences between a SharePoint Foundation 2010 and a SharePoint Server 2010 installation are regarding the deployment of language packs and updates. Language packs as well as updates and Service Packs for SharePoint Foundation are different files and smaller in size. So you need to download the right ones.