Over the last year, I have been slowly pushing patches upstream to Vagrant introducing native Haiku support. Vagrant is an open-source tool to build and maintain portable virtual development environments. Essentially, Vagrant lets you deploy and rapidly customize a Haiku virtual machine with programmatic scripts.
If I understand this correctly, this is the easiest way to setup a Haiku development environment. As someone who intends to snag up a decent used laptop to fully dedicate to Haiku, I will do whatever I can – no matter how little – to entice people to create applications for Haiku.