There are several options available for licensing Microsoft systems on a HomeLab.
Many Microsoft products are available with 180 day evaluation licenses. Additionally Technical Preview versions are often available for upcoming platforms.
Microsoft offer several SKUs of the Microsoft Developer Network subscriptions, however several of them (including the most suitable- MSDN Platforms) are only available through Volume Licensing, which may not be suitable for a Homelab environment.
Exact details are subject to change so check the MSDN website for the latest details and what is best for you, but as an example in April 2016 Microsoft offered "Visual Studio Professional with MSDN" which includes perpetual Windows (Client + Server) and SQL Server licensing for $1,199/£825 list.
If you are a student or faculty at a qualifying institution (basically a School, College, or University) you should be able to get Imagine licenses (formerly known as DreamSpark and before that MSDN Academic Alliance). There are three tiers; the free offering (See here) gives you the Windows Server and SQL Server licensing and some applications. It also includes some development tools (Visual Studio etc) and Azure credits.
There are also two paid tiers, Standard and Premium, with a small annual charge paid by the institution. These give a wider range of products, a Premium subscription provides almost the entire Microsoft portfolio, usually with the exception of the core Office suite.
The standalone Hyper-V hypervisor (without a Windows Server OS) is available free.
Obviously you could also visit your local computer shop and purchase full retail licenses, but this is probably the most costly option here.