If you are really thinking about building your product you should first do the alpha and beta. There is a strong community of tech people on Hacker News, ProductHunt and Reddit that will support your idea and even pay in advance if you can show a demo first.

Give you an example: Dropbox. Drew (CEO) made this short video https://www.youtube.com/watch?v=7QmCUDHpNzE about how Dropbox was supposed to work. He send it to all the community and it becomes viral. Everyone started to sign up. He had a fremium model at start, but look at it now.

So I will encourage you to do two things:
Follow this order
1-Go and build your alpha/beta and create a demo that everyone can see and feel excited about
2-Share it with the community
3-If you want to "sell it" in advance you can use selz.com or payloadz.com

And rethink you business model and moentization strategy so it adapts to your product and not the other way.

:) If this helped let me know!