this all depends on the countrys laws. in germany you can't be evicted even if you fail to pay your rent. the landlord has to go through a lot of effort before they can kick you out.

also, the landlord has NO right to enter the property unless there is an emergency, and even then they may have to break the lock to do it because the lock may be changed, and the landlord may not have any keys.

we also did replace windows in one place we lived, and completely rewired the electricity (which included putting new pipes into the walls to hold the wires). it was an old building, and the change was made in consultation with the landlord, but there is no reason it can't be done.

apart from that any change that doesn't change the structure and stability of the house is possible, and any change that an easily be reversed in most cases doesn't even need permission of the landlord.

in another apartment we added a hardwood floor on top of the floor that was there. a sheet of foam and the hardwood on top. for the first room we paid a contractor, for the others we did it ourselves.

if my pension is not enough the government will chip in with housing allowance to make sure i can pay my rent. at worst they will ask me to move into a smaller home if i happen to occupy a place large enough for all my kids who have long moved out and no longer need the space.

i won't be living on the street and i enjoy the freedom to move whenever i like without being tied to a particular location.

also, being a landlord and renting out your property in germany is so onerous that it's not worth it unless you are doing it as a full time business.

that adds a further point in favor of renting because you can't just buy a property and rent it out without putting a major effort into maintenance and paying for upkeep.

finally, as long as you own property you generally don't qualify for financial support, should you ever need it

it's all a matter of perspective.