The decision to pursue patents, which kind and how much to spend is a business decision that merits consideration and planning.
Although you can do it yourself you will probably regret it later. But then, you could spend $25k+ with a patent attorney and regret it, too. Patent services are like medical care. Cutting costs now can result in huge costs later. Often, you won't know about the problems until later, and by that time the situation is irreversible. The cost for a typical US patent, from start to finish, is typically between $10 and $30,000.
The patent process is like a tennis match. To get a normal, US "utility" application prepared and filed ("serving the tennis ball") you are probably looking at spending $5-20k on an attorney depending on the kind of invention.
About 1-4 years after you serve, the patent office will return the serve. You will have additional costs for hitting the ball back. When the patent office agrees to grant the patent, there are additional costs for the final processing. All told, after filing the application, the follow-on costs are typically in the $1,500-15,000 range (depending on lots of factors).
The US patent process typically takes 1-7 years. The current published average is almost 3 1/2 years.
There's also the option of an informal provisional application, which typically runs $2,000 or less. The provisional expires in 12 months and there's no tennis match. Provisionals generally don't provide much protection, but they are great to get "patent pending", to establish a date of invention, and to set deadlines for making a formal application.
Lots of people like to file provisionals to get their feet wet and during initial market tests. If it looks like the product will sell then they decide whether to pursue a real patent.
You might also want to consider pursuing a design patent. Typically this costs about $3,000 to start and issues in 12-18 months. Design patents are supposed to be for the ornamental/ artistic/ non-functional aspects of products, but lots of people use them as a cheap way to protect a product's appearance.
Patentability requires that your invention be new, and also that it is something more than an obvious variation or modification of the prior art. The US courts and the USPTO are getting tougher on the obviousness standard.
A "prior art" search should be one of your first steps in the patent process. In the US, the prior art mostly includes (a) any patent filed prior to your invention, (b) any publication (e.g, magazine article, web page), published more than one year prior to when you file your patent application, (c) any public use, sale or offer to sale of the invention by you or anyone else in the US more than one year before you filed your patent application. There are some other categories -- the patent laws are filled with gotchas. From these three categories, you can see that even if someone else hasn't gotten a patent on your invention (or if they did and it expired), you still might not get a patent either.
The patent law also has gotchas on deadlines. The US and foreign laws favor early filings. Tread carefully here. If you file the application too late, you might lose US and/or foreign rights. Most foreign countries have "absolute novelty" rules, which bar patenting if there has been any kind of disclosure of the invention anywhere. The US has a one-year grace period on the absolute novelty rule. The rules are quite complex so don't rely on this simplification. The safest approach is usually to file your patents prior to any kind of public disclosure or attempt at commercialization.
Now, back to searching. Before you spend the money to hire someone else, try doing some searching on your own. Use a search engine such as Yahoo to see if there is (or was) anything out there like your invention, or articles which are on point. You should also use the patent database of the US Patent & Trademark Office www.uspto.gov to search issued patents and published applications. Most people search and find nothing, but at least it's a good start.
While there are still some professional prior art searchers, it seems like most people just have their patent attorney do the search. It is usually more efficient and accurate.
Be sure to pick a patent attorney who has some familiarity with your technology. We patent attorneys usually specialize. You probably don't want a software expert working on a new pharmaceutical.
These estimates are budgeting guidelines based upon having a competent patent attorney doing the work, and include the government fees and other costs. You can look up the government fees at www.uspto.gov
Though you only asked about patents, you should ask your IP attorney about copyrights and trademarks, too. Many products can be protected by copyright and trademark in addition to patent.
Hope this helps. My email address is public. -Steve
15 years of experience as an intellectual property attorney.