Good offer for a young family? Buy yes or no

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The heating system is unfortunately an oil heating system and it would also come "iwann" someday.
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Every heating system comes "iwann" :)
If the system is designed for low temperature, as far as I know it does not have to be replaced after 30 years due to an ownership change, although it would certainly be necessary - and sensible - then. Especially because of the new CO2 tax. The storage space provided by the oil tanks could be used for pellets. Or by then fuel cell technology will be ready for single-family homes.
But (!) a new heating system costs a lot of money, for which reserves have to be created. This also has to be done for other things.

That was the info on this. Maybe he can explain it in more detail...?!

There is also a house in my family that is being sold. And only to a family with children. Preferably with the grandparents moving in as well. They are now waiting for the offers and will then decide. The house will not be sold to the highest bidder, but to those who fit into the neighborhood and meet the criteria.
The grandmother died a few years ago and the caregivers were allowed to live there for free for years and only had to pay the additional costs as well as take care of the maintenance. The family also helped them with finding an apartment.
Money does not always rule the world.

Would she get her nails done if it didn't make her happy...?

You might misunderstand me. What I meant to say is that one shouldn't deceive oneself into thinking that one only needs colored fingernails once a month and nothing more in their future life. Of course, one likes to have or experience beautiful things for oneself. I was referring to the idea that colored fingernails alone would be enough, that the woman or oneself doesn't need more. TOGETHER one must find a basis to deal with it appropriately, because as soon as one person calculates something for the other, it gets bad. BEFOREHAND and TOGETHER, those are important magic words!
If that alone were enough, life would be simple.

But watching the other and pushing them to give up their beloved things only leads to arguments.

...and suddenly a house is offered online again. Therefore, everyone should FIRST check themselves, exactly. Once you have arrived there, it gets difficult anyway or you haven't done your homework beforehand.
Anyway, I think life changes on its own when you have a house. Suddenly you do things that you never did before, and some considerations take care of themselves.

Whoever sees restriction as a loss of quality of life should better leave it alone.

That hits the nail on the head.

There is also a house in my family that is being sold. And only to a family with children. Preferably also if the grandparents move in. They are now waiting for the offers and will then decide. The house will not be sold to the highest bidder, but to those who fit into the neighborhood and meet the criteria. The grandmother died a few years ago and the caregivers were allowed to live there for free for years and only had to pay the additional costs as well as take care of the maintenance. The family also helped them find an apartment. Money doesn’t always rule the world.

Since you already quoted me, I will answer you too ;) I never claimed the opposite but showed the part that roughly answers her question. Roughly because even "rich" people have nothing to give away and there was nowhere anything about family, so her inquiry is quite justified, even if only as a marginal note.

I once encountered someone like that when it came to a rental apartment. I did not get the contract, but the rent asked was certainly about 30% below market level. It was just a wealthy lady who also personally met the rental applicants. I am always pleased by such things when there are people who are not primarily concerned with the best possible return. When the house is finished, I will rent out my condominium as well. Unfortunately, I am not rich, and my financing forces me to ask for a market price. Otherwise, I would also charge a more moderate price for friends or acquaintances. In the position of the original poster, I would also accept the offer. Such an opportunity probably won't come again. Possibly consult a financial advisor to get better terms, if that is even possible. But soon commit to the seller, so that he doesn't change his mind or another family is simply quicker. After all, nothing is signed in blood. You can always say until the notary appointment that the financing does not work or whatever.

to give away and nothing was mentioned anywhere about family, therefore her inquiry

Sorry, I thought the question was about why a wealthy person would sell a house so cheaply and that there might be a catch.
The OP wrote that the house seller probably does not have to sell.