Great question. You can link from one site to another through another article/page/post I think this is how I would do it.

Just keep one site. :)

Hi Dudoni,

If you were to use the same content , write a new one first and put a reference back to the original content - this helps you to amplify your niches. I am not sure if I am replying your queries correctly - if not please ignore.

John.

I would put the content on one site or the other...I wouldn't even bother rewriting it because that is typically more difficult than creating a brand new page/post (believe it or not).

Post it on the site that will work best and then move on.

As Ken says, re-phrase

Yes it is considered duplicate .
You can change the wording for the second article with the same idea.
Ken

it would be considered as duplicate content, if you can rewrite it for the other site would work better

I would rewrite/paraphrase the content just enough that it speaks to the demographics of the two different niches. Copy and paste, while if it even IS your own original content, would look to Google like copycat material. So alter it just enough to give the same content, but said in a modified manner.

Not sure I have the answer but am sure pothers will.