House construction on an existing plot, return?

Since I only finished my studies a few years ago and my professional future can theoretically continue elsewhere quickly, I did not want to commit locally. Therefore, a new build with a land purchase is still not an option for me. However, the desire for self-fulfillment is growing more and more.

Now it also appears that one can possibly build on existing land or buildings. This would save the cost of the land. I would like to take advantage of this opportunity if it works out as planned - but that is rarely the case.

The house should be relatively small (about 100-120m2), sufficient for two people. No basement, but preferably bright and large rooms, no luxury but also no laminate flooring.

I have two central questions in this regard:

- What is the price range (with an architect or as a prefabricated house)? I would like to pay off the house with 50-70,000€ of equity within 15 years (max. 1,500€ rate, but rather as a special repayment to remain flexible).

- I think that with a single-family house that one rents out after a few years, no profit can be made or one will lose money with some bad luck. However, if it should happen, for example, in five years that one must move and rent out, could the house still be financially "utilized"? Or can one barely recover the costs for construction, financing, and maintenance even without land costs? It should be noted that the house would not be built near a large city, but prices in the area are noticeably rising (major infrastructure programs).

Of course, I am aware that this question cannot be answered easily; I am more interested in opinions or experiences.

1. Construction costs The first rule of thumb is 1800 to 2500 euros per square meter of living space. Although I can never remember whether additional construction incidental costs are included or not :P. However, this can be found quite easily here in the forum and elsewhere. The annoying thing about this is: especially small houses do not become cheaper in a linear way, as many costs are incurred regardless of the living area. 2. Return Whether the plot of land is already owned or still has to be purchased is irrelevant for this question! In a profitability analysis, the plot must be valued anyway.

It mainly depends on the location of the property. As you describe it, I wouldn't really expect any returns, but maybe you'll break even more or less if you practically include the property.

Now it also appears that one can possibly build on existing land or buildings. So you would save the cost of the plot of land. I would like to take the opportunity if it works out as planned - but that is rarely the case.

However, the desire for self-realization is growing more and more.

I don't believe that one can realize oneself like that.