If you want the most size for your money go with a 45 mil epmd rubber liner, you can buy them for pretty cheap, most home depots offer them on a roll. Cut to a specific size. You can also buy them there from companys like Beckett or whatever the store carries. The liners are fish safe and gaurenteed for 20 years. Dig yourself a hole, and line it with pool sand or old carpet. I would buy a pond book, or magazine and research it. You will also want some sort of bio-filter, they come in both in pond or external models. For a 1,000 gallon pond you won't need much more than a pump rated for 1,000 gallon pond ,bio filter,and the liner itself. Not very expensive at all. It's the fish and plants that cost you LoL. It is very addictive as is any type of fish keeping.