Hey @Thomas_Mahon - I came across the exact issues as you did, but trying to build DynamoCore the other day.
It should be as simple as cloning the repo and clearly documented steps…this clearly isn’t the case.
To get Dynamo (Core at least) to build on Windows 10 and Visual Studio Community 2017, aside from the pre-requisites listed by @Kulkul, you also have to install the .NET 3.5 SDK add-on, search for “Visual Studio Installer” on your PC (comes with VS2017) and then add it from the “Individual components”.
As @Konrad_K_Sobon mentioned, installing Visual Studio 2015 is a good idea, seemed to have resolved some of the issues I was facing in VS2017 as well.