A Search Can be Used to Save Costs!

It is important to note that a search of the prior art in not a prerequisite to file a patent application. A prior art search helps to determine the bounds of your invention and could help to decide whether to file the patent application or not.
Now just what is "prior art"?

A "prior art" reference provides an enabling disclosure and thus anticipates a claimed invention if the reference describes the claimed invention in sufficient detail to enable a person of ordinary skill in the art to carry out the claimed invention; "proof of efficacy is not required for a prior art reference to be enabling for purposes of anticipation." Impax Labs. Inc. v. Aventis Pharm.Inc.
For instance, if the prior art search shows your invention just the way you had envisioned it, then there would be no point in filing for an invention. That prior art anticipates your invention.
On the other hand, let' say you find little or no prior art. Then, there is a good chance for having a patentable invention since that prior art to anticipate your invention has not been found.
A search of all previous public disclosures should be conducted to determine if your invention has been publicly disclosed and thus is not patentable.  A thorough patent search is difficult since patent searching is a learned skill. A video on prior art provided by the USPTO is linked here.

Tyrean is a useful resource for your patentability search. After an application is filed, the USPTO will conduct its own search as part of the official examination process.