Dude, I dont live in the States, I'm Canadian. In my backyard, my father and I built a liner pond for about 1800 dollars. Liner, rocks, filtration were the biggest costs. Took a weekend to build, I dont know how many gallons it is but its about 9 feet long and 4 feet wide by 3 feet deep. Theres a smaller 100 gallon pond that waterfalls down into the main big one as described above. I've got about 14 Koi in there total. 3 - 1.5 footers, 4 1 footers, and about 7 - 5 inchers with about 10 feeder fish aprox. 5 inch average. Everyone seems to be growing and healthy... everyone survives winter too.
Also, you can cut those costs by making you're own filtration box, we paid like 400 bucks but we were suckers, we realized we could build our own for like 50 bucks using rubbermaids or smaller garbage cans... look into DIY, saves lots of cash.
As for plants, although illegal, we went to the nearest marsh and grabbed a few lillies, cattails and other grasses.
Good luck, post some pictures please!
Also, you can cut those costs by making you're own filtration box, we paid like 400 bucks but we were suckers, we realized we could build our own for like 50 bucks using rubbermaids or smaller garbage cans... look into DIY, saves lots of cash.
As for plants, although illegal, we went to the nearest marsh and grabbed a few lillies, cattails and other grasses.
Good luck, post some pictures please!