Welcome to Rebreather World.
While building your Rebreather can save you some bucks and (usually) means you'll know your unit inside out, I would only think of it as a good idea if you really have the skills and equipment to build a rebreather.
Sven on the other hand makes a good point, a used CCR in good shape can be found for considerably less money than a new one. Even a new Sport Kiss costs roughly half of a new Vision Inspo.
I was in a similar spot, couldn't afford a CCR for quite a while. Considered a semi-closed rig, but rather waited and saved a bit longer and got a Sport Kiss instead. It was certainly worth it. If you get a chance to try both with an instructor you'll probably agree.