Now, if you're talking about raising an actual tenant, that's a different story
Raising the rent on existing tenants is the topic of this thread. On that note just a recent anecdote: a friend told me his brother has 8 kids and is well behind on tuition and bills. This brother helps him out a bit but he is struggling month to month. One source of his income fell behind on paying him, making a tough situation worse. He has a tenant with a successful online business who’s wealthy father in law is paying the rent.
His brother is still charging this tenant 13xx a month, with similar apartments in the (hot) neighborhood going for over 1900. The yungerman in the basement down the block was just raised to 1900. My friend told his brother that is unfair to his own family to leave so much rent in the table. He went to one of the Roshei Yeshiva in town (not a posek) to ask if he should raise the rent. The Rosh Yeshiva told him that based of what the Chafetz Chaim writes he should leave the rent low and trust in Hashem to take care of his parnassa.
I don’t know if the Rosh Yeshiva was made aware of the fact that his kids schools aren’t being paid and that the tenant is far more well off than the landlord, but that was the answer he was given.