Yeah, thats how it is in Germany, although they may not have a house, they will most of the time get enough pensions to afford their daily lives.
I am an adult, but my mother would rather give me money than the other way around, but my parents are also upper middle class.
But if my parents ever needed money to survive I would support them, its just unlikely to happen.
Ok, thats a bit different, if the house is somewhere where noone wants to live anyway (and if they want there are enough options available), then it really is ok morally, at least for me.
One could argue that the space should be used for farming, but that depends on how big the property even is if that makes a difference at all.
If it has a really big property with lots of grass it would be a good thing to rent that part out to a farmer. If it is more of a forest its probably better if it stays that way.
I would say owning it while not using it very much and not renting it out is the least ethical choice as no one can use that house.
The most ethical option besides not owning it is renting it out at a reasonable price, so someone else can live there and you are not squeezing every last dollar out of them.
I would send him the money if he cared for you as a child and not abused you, and you can afford to send it to him and he really needs it.