You could always find a good deal on craigslist. I just saw a 135 gallon tank, stand, and canister filters for $200. Not that expensive to start up a tank for a mantis shrimp. Lights to grow corals and protein skimmers are what drain people of their money! Both of which you don't need. It would be cool to do a display refugium type tank. Have all different types of macroalgae and the mantis shrimp.
“Success is walking from failure to failure with no loss of enthusiasm.”
- Winston Churchill