I've been working on a side project for the last month and a half outside of working hours. This is a product in the same niche with everything in my company's portfolio and is strongly related to our line of business. The idea is not exactly original - it has been coined by a high-ranking employee at one of our internal hackathons as a sample project idea. Moreover I've received numerous inquiries for this functionality by our existing customers while handling their support requests.
Unasked, you've volunteered your own time to develope an idea suggested by others.
I'm ready with the MVP, and I've scheduled a meeting with my manager ...
Might have been an idea to ask your questions and be ready first.
- What is the best way to approach my manager about this?
Develop your plan first, and have everything ready; unless you're just looking for some feedback. You don't want to present a half-baked idea.
- What benefits can I expect if they do, indeed, decide to adopt my project?
Lavish vacations on the Riveira, and steak for lunch with the owner.
Seriously, it's rare for ideas to be adopted; if it was such a good idea and needed the company ought to have been working on it already.
We don't know what your idea is or whom you work for, we could only guess how it would be received and compensated - think positive is good, but you want the positive response from your management not us (inflating your hopes and dreams). See the 'Riveira Link' above, no guess for that question.
- Would it be reasonable to ask for a pay raise or a single time bonus?
A raise probably lasts for as long as you stay and may or may not lower your next raise.
A one-time payment may or may not cover the hours spent nor will you be compensated if it sells a million copies for ten bucks a piece.
You can ask for Stock too.
You ought to have checked what they thought before investing your time and effort - if that were the case you'd have some idea what they'd think and know what you stand to gain.
You're basically saying: "Here, I made this; what do you think ...'.
- What's the best course of action if they decide that they are not interested in the project?
You can ask what it would take to become accepted.
- Should I ask for permission to release this to the marketplace on my own? If that's not feasible should I ask to make the project open-source and release it for free?
You could, but if they think it's their idea to be developed when and where they choose, and by whom they select to do it, you're risking some ill will.
- In general what to do with this project if it gets turned down?
You should have asked first.
You might have wanted to have worked on your own ideas on your own time and kept everything for yourself.
You're betting they're gonna like it, and that you'll recoup some modest reward.
You've done the work, scheduled the appointment and at the 11th hour you ask: "What do you think?".
Smile, and good luck with that.
You would have likely made more developing for yourself.
They're going to wonder if you've incorporated any of their proprietary technology into your project, they'll probably ask to see it.