Patent Searching Tips for Inventors

"Nearly any patent professional will recommend a formal patent search before filing a patent application. While a search is costly, it can actually save money. A search can reveal that someone else already invented your invention. This knowledge saves the time and expense of filing a patent application that would later be rejected.
If you're interested in saving the money involved in a formal search, you may consider doing an informal search yourself. If you find that your invention already exists, you will save the cost of the formal search."

There are several methods for searching for patents as explained in this PHOSITA post.