the question of how to build a pond is usually going to involve man made pond construction unless you are asking a beaver. Ok I will be serious now. Here is a resource for the price of building a pond . The answer is quite varied depending upon your goals. Do you want a swimming pond , a natural pond or a plastic lined pond ? Each of these varies in cost from a couple thousand dollars for an unnatural plastic pond, up to tens thousands for a very natural swimming pond.
While a do it yourselfer might take on building a pond, the question of how to build a lake is much more complex with much greater risks. Again it completely depends on your quality goals. After you review your goals, then you can be presented with budgets to reach them.
One last note, beware of most of the internet information on this subject. They may be well meaning, but most lack any real experience.
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Other people asked questions on various topics, and are still waiting for answer. Would be great if you can take a sec and answer them