When I got the idea to build a water feature, the first question my wife asked was, "How much will it cost"? That shook me into a reality check. How do you figure out the cost of something you have no idea how to construct? So, I came up with the idea to draw it out on Google Sketch-up. I diddled around with the design and eventually figured out how much rebar, chicken wire, livestock fencing, quick-crete, sand, cement blocks, field stone (concrete chunks were substituted), rubber pond lining, and how big of a tank, pond, and pump the project would take. The sketch-up drawing really helped to visualize and scale out everything. I was able to even calculate how much water would be flowing through the system at any given time, which determined the size tank and pump I would need. I do wish I would have spent the extra money and bought a 300 gallon reservoir tank. That is the only regret I have. As I brought my idea to realization, I researched ferro cement, water features, waterfalls, streams, pond plants and landscaping, and pumps on Google. I watched endless videos on You Tube also. I would recommend "Ponds gone wrong" which is a series on You Tube produced by "Pond digger". You will learn tons of info from there. Look at everything you can find about ferro cement. That was the hardest subject to pin down and get an exact mix on. I finally experimented with sand mix, mortor mix, and portland cement and got a good texture that would trowel out and stay in place.
The actual construction took from May 1st to June 9th. I had about 2 months of research, planning, and cost estimating. The whole project cost was about $6000. That doesn't include labor, dirt, sand, or concrete chunks or rocks which we got for free.
I hope this helps. Let me know if you need more advice.