2 sites, same niche: how many BLs should I make?

Hi all, I have 2 sites ranking well on the same niche.

Currently, there is only 1 backlink from the biggest site to the smallest, linking from and to a page on the same topic that ranks well on Google for the same keyword.

It's as if I had both domains house.com and houses.com and linked from house.com/best-house to houses.com/best-house-to-buy

Now, I am wondering if I should build any more backlinks than that or if I risk being penalized by Google. Also, shoul I only build links from one site to the other or can I do reciprocal links? How many links are too many? Isn't there any risk of Google seeing me as a PBN, even though I only have 2 sites and they are both "legit" with quality content.

Any thoughts? Thanks

there's no definite answer to the question "how many links are too many?" because it depends on a lot of things.

And I wouldn't build more than 1 reciprocal link between both sites either. Just hope that google never figures out what you did, or else bye-bye rankings!