I would worry less, at this stage, of whether or not you have the money to develop it or market it. Instead focus your energy on getting to understand the sector it’s in. The more you understand about the market, the more you will be able to understand your inventions’ role in it.
Not having any clue as to what it is makes things difficult! Is it a gadget, an appliance of some sort? Is there a computerised or electronic element to it? You talk about building a prototype. Is it something that can be 3D printed, as a cheap prototyping start?
Why has no one come up with the idea before? Is it genuinely needed/wanted. Was prototyping too expensive before, is it more feasible now with 3D print option.
Sorry, it’s difficult for me trying to come up with ideas or advice without actually knowing what your idea is. Bit tricky to even know if you’re running in the right direction.
Why don’t you start by putting it all down in writing. Develop a brief summary of it. Just for you initially. Don’t think too far ahead. Start developing a document and get your creative ducks in a row. Once you’ve created that you may be inspired to take another action that will lead you to more answers.