I love DIY projects, so I say go for it! But....
...you should consider that it'll probably cost you as much as, or more than, a store-bought tank of the same size. You likely wouldn't save any money unless you were building a really large tank - like 250g or more.
Again, I'm all for DIY but I just wanted to point that out in case you're considering this idea with the thought of saving a lot of money. You can, however, save TONS of cash by building your own stand and lighting hood.
Cheers