Is purchasing a house and complete renovation affordable?

My (large) detached house is situated on a 600m² plot and subtracting the garage, driveway, trash bin shed, stairs, paths, eaves strip, etc., I still have 260m² of green space left. So with 300m², there is nothing left that is inherently (i.e., by the area) strenuous.

Easy to maintain is less a question of size and more of the layout. If everything is supposed to look like the gardener was there yesterday...
And the other question is whether, with 290 sqm minus house, parking spaces, terrace, paths, garden shed, the garden can even still provide what one expects from a garden. There isn't much space left, nor privacy. It's effectively a balcony with a few bushes

For us, it's mainly about having a bit of privacy... I can go out into the garden and no one around is watching me directly.
In most new housing developments, houses are lined up one after the other. Sure, they have a small lawn area, but everyone can look into the garden and even into the house.
That is no longer privacy for us.

Going out into the green, putting up a sandbox and a swing for the children, and a bed for growing vegetables, and then we are happy.
In the new housing developments (at least here), that is not possible.
Everything is cramped together, walkways run all around the house, and you feel watched.
There are also plots where that is not the case... but these are unaffordable (300,000 and up) or not even available.

I can well understand that, it was important to us too. We moved far out into the countryside where land is still cheap, and bought two small plots and had them merged. This way we have the opportunity to let some greenery grow in and hopefully in a few years we will have some nice privacy there. Even though we have very nice neighbors, it does have something to do with feeling comfortable when you feel somewhat protected.

My (large) single-family house stands on a 600m² plot and after deducting garage, driveway, garbage bin enclosure, stairs, paths, eaves strip, etc., I still have 260m² of green space left. So with 300m² there is nothing left that is per se (i.e. by the area) exhausting.

And most new building plots are a maximum of 350 square meters in size.
And prices of 1000 euros per sqm have already been asked and also paid.
Of course not with the current interest rate situation, but you still have to reckon with 600-700 euros per sqm.

I think it always depends on the current life situation what one wants. I can understand the objection that after 25 years one may no longer be willing to maintain such a large garden. But we are both still under 30 and have no children yet and want to be able to offer them a garden for playing or something like that. If I were to build in 15 or 20 years and the children were of a corresponding age, of course we would have other priorities... but I don't think there is a perfect house with a garden for every stage of life.

No, the perfect house does not exist, but there is a healthy middle ground. Between 300m² with a doghouse in the big city and 3,000m² with a 250m² villa in the sticks, there are some shades of gray. I would therefore rather focus on small towns, with reasonable plot sizes of 600–800m². Kids or not, the outdoor area must be maintained... in case of doubt, as a full-time working couple, you have no time for that and later in old age no desire or no possibility anymore because the body does not cooperate. The question is also always what happens with work. In my opinion, the future does not lie in 100% remote work... there may be some people for whom it works well... whether for a few years or until retirement. However, the majority will have to go to the office occasionally in the long run. We are currently reintroducing office days because things are drifting further and further apart... If the commute to the office then is 200km, good grief...