Initial ideas for building a small house on a backlot

If you really mean small,

? It said something about the desire for a 14 sqm utility room…

If you really mean small, then here is a suggestion.

looks good, but the utility room is missing and according to a podcast I’ve been listening to quite often lately (I know, not a valid source of information) “Hausbautipps mit flo vom bauherrenforum” the utility room should be about 13sqm, for heating, solar storage and so on... I’m happy to be proven wrong - most prefab house providers are rather around 6-10sqm.

When she had finished her studies, the house was supposed to be sold but it was really hard to find buyers. Everyone either thought the house was too small or the plot of land too large.
In the end, they just barely managed to sell it for the original construction costs.

we have already found a house in the perfect size and layout (80 sqm over 3 floors). However, the owners had the idea of getting the full purchase price now and then living there rent-free for at least 1 1/2 years. I don't know if they also think they can't sell the house because it's "too small."

According to a podcast I listen to quite often at the moment (I know it's not a valid source of information) "Hausbautipps mit flo vom bauherrenforum" the utility room should be about 13 sqm,

A more valid source than the "colleague" Schoen you will hardly find, after all, he has been part of the "Fertighausexperten" team for several years now, which I always like to recommend.

we have already found a house with the perfect size and layout. (80 sqm over 3 floors) However, the owners had the idea to first get the full purchase price and then live in it rent-free for at least 1 1/2 years. I don’t know if they also think that they won’t be able to sell the house “because it’s too small.”

The combination with the three floors makes the difference. Finding a buyer conveniently before the planned moving-out date does make sense – but conversely, probably not the desired payment timing for you. The discount would of course have to be right.

You will hardly find a more valid source than the "colleague" Schoen

Ah, good to know. I’ve always found the info in the podcast good and interesting so far :)

The discount of course would have to be correct.

At first they naturally wanted no discount. In the end, the offer came with a maximum rent of €800 p.m., and that was just too little for us. With the current interest rates, we would have had to "pay on top" around €600-700 per month, in addition to property tax, our own rent, and so on. We would have bought it by the end of next year (purchase price next year) :D

I’m not an architect, but we roughly imagine the layout like this, then we would be at about 90 sqm :) :

That would only be true under the assumption that are available in unlimited quantities. But they are not; their number remains the same, regardless of what is built on them. Just a little food for thought…

The advocates of the tiny house idea have not yet realized this with the unchanged quantity—they are putting pressure on demand. Building a tiny house on a normal house plot only relaxes the sealing issue on the level of the floor area ratio of the individual plot—but not on the level of the development areas. So land consumption remains the same, even if it may look averted in the naive calculation. A tiny house is essentially a detached apartment (or even a maisonette). Anyone who wants to save space ecologically and economically cannot avoid multi-family houses. I could imagine that political steering would in the future prefer semi-detached and two-family houses, possibly already in the development of building areas.