We built on my parents' property. We had no other options because building plots here are a) scarce and b) hardly affordable.
The property was divided; our part was then allocated proportionally between me and my husband so that it also reflects our contribution to the house. I own more because I brought in quite a bit of equity; my husband none at all. The remaining amount was financed equally by both of us. Currently, my mother, who lives next door, still has a right of way over our property and is basically the main user of our carport. Her garage, which was there before, had to give way to the construction, so she now parks in the carport, and we are fine with the less "nice" parking spaces around it. That works for us. Access to my mother's house is via our carport. This right of way expires upon my mother's death. That means: if we ever rent out or sell my parents' house, there will be no more right of way. When renting, we will either have to find a solution for how the tenants get to the front door or accept that they have to walk through our carport. We'll think about that when the time comes. There is also a sewer easement because the sewer for my parents' house runs over our property. This right is tied to the existing house, so if a new owner ever tears down the building, they must install a new sewer and may no longer use the one running on our property. As long as the house remains, the sewer stays as it is, and so does the corresponding right.
My mother herself had a rather intrusive mother-in-law and therefore consciously keeps a low profile. It’s more like we say: now we really have to check in with them! My parents-in-law – who live about 10 km away – are more clingy (but I get along well with them, so no problem there either!)
What I want to say is this: it can definitely work out well, but you should really have everything concerning the property notarized. Rights of way and sewer easements do not have to be registered for eternity but can be tied to lifetimes and houses.
It depends very much on how well you get along with each other. Things work well for us. But it doesn’t have to be that way. If my mother were constantly showing up at our door, I would go crazy!
If I have read this correctly here, the father-in-law would pay for the demolition, right? So, then it is indeed a figure to think about – €30,000 makes a difference when building or not.
For me, the decisive factors would also be the plots themselves: size, location, condition? A parcel in a new development area or a larger plot in an established neighborhood? Well... personally, I’d prefer the latter.
There are just many factors, so really no one can give you good advice here – only food for thought. The decision is always very individual.