SolutionDirectory
 |- MainProject
     |- MainProject.csproj
     |- Main.cs
     ...
 |- FirstSlaveProject
     |- FirstSlaveProject.csproj
     ...
 |- SecondSlaveProject
     |- SecondSlaveProject.csproj
 ...
 |- BuildFolder
     |- MainProject
         |- bin
         |- obj
     |- FirstSlaveProject
         |- bin
         |- obj
     |- SecondSlaveProject
         |- bin
         |- obj
     ...

<PropertyGroup>
  <OutputPath>$(SolutionDir)BuildFolder$(MSBuildProjectName)$(Configuration)-$(Platform)bin</OutputPath>
  <IntermediateOutputPath>$(SolutionDir)BuildFolder$(MSBuildProjectName)$(Configuration)-$(Platform)obj</IntermediateOutputPath>
</PropertyGroup>