If you install good new quality parts, it's gonna cost you more to build from scratch. If you got a guitar bone yard in your garage you probally can get by.
A Jagstang....
Home made Body/Paint - $100
Neck - $150 - $200 (more like $250)
Tuners - $30 - $60
Tremolo - $60
Pickups - $100+
Pickguard - $50
Control Plate - $10
Electronics - $30+
That's a rough estimate of $500 - $600. Surely you can find a Jagstang for around $350+, if you look hard enough. If you hit craigslist hard, you may be able to a deal. I got a toronado, tele & duo sonic this week on the list, for a good price... but I just don't see offsets/shortscale guitars listed them much there.