Invention patent: why bother?
Why indeed? Considering how expensive and time consuming it can be - potentially many thousands of pounds/dollars over a few years - it's worth thinking hard about whether you really need an invention patent or not. Save for in highly technical industries like pharmaceuticals and genetic research, the majority of inventors, in Britain at least, are in the middle ground. Not working on their own, but not working for a massive company with bags of cash. That makes it a serious step to take, and one that's worth getting professional advice about. There are other ways to protect your ideas, such as trade secrets and copyright laws. Copyright, for example, attaches as soon as you come up with an original work, although it's a bit more complicated than that to enforce it. However, if you have a brilliant idea that people would be interested in making use of - and, more to the point in the current context, copying - a patent is the most powerful legal tool.
Say you've invented a machine which runs on antimatter in your shed (there might be a few issues with this, but we'll skirt over them for the sake of it being a catchy example). Assuming you're going to use a patent lawyer, which is wise, you can expect to pay several thousand dollars for any invention patent application, and the more complicated it is, the more expensive. It could run into tens of thousands for something really intricate like, say, a machine which runs on antimatter. And although it's supposed to take about a year for the application to go through, there's a perpetual backlog, which could bump up the cost. If you abandon the process halfway through you won't get your money back, so is it worth it?
For something as revolutionary as this, it's probably worth begging, stealing or borrowing the money but it might not be as clear cut for another invention patent. One solution could be to file a provisional application while you work on it some more - that's only a quarter of the full cost and as long as you file the full application within a year you have priority over any rivals. There are other options, such as spending what money you have on branding and advertising and simply keeping your invention a trade secret. If it's something that would be difficult to reverse engineer, i.e. work out how it's made, that could work well.