VGFacts

First on my list - The Legend of Zelda: Parallel Worlds and TLoZ: Godess of Wisdom.

Any suggestions?

Brutal Mario.

What do you mean by "investing" in it? I quite don't understand.

In before cease and desist?

I've read about people re-programming games. Google Zelda Parallel Worlds and the links will give you an idea of what I'm talking about.

Making your own personal projects based on existing games? That I can help you with.

No. As cool as it sounds, I don't have the time for that right now. Or a computer.
I have found games on Amazon and eBay for sale. Is that copyright infringement or are there loop holes?

You are looking for "cartmod" games ?

I have found some. For sale.

I think that's called buying a bootleg. While they are on Amazon, they aren't officially licensed by Nintendo so it's probably illegal to make money from an already existing IP.
Even then, ROMhacks are (should) be free anyway.
I wouldn't bother with paying money for them.

...I wouldn't.

There's some games like this one too:


And others that were canceled just before there release:




And others who never left Japan (fully translated)