Prefabricated house construction period - What should I expect?

We definitely keep an eye out for existing properties, but the market in this region seems quite sparse (at least with what we imagine).

Although I hate real estate agents like the plague, I can only recommend it to you here. The good houses hardly ever or never end up on Immoscout and the like because the agent offers them to potential buyers, and they take them immediately. Only private houses end up on the internet (depending on the region, few, because there is no reason for the seller to sell privately) and the houses from agents that no one wanted. Consequently, you have to check the files of one or more agents.

For me, these offers sounded incredibly simple: We buy land + house from the provider (of course, as long as both fit) and then it starts!

That is doable, no question. But you do have to have some knowledge of planning (ok, understatement), have the time to waste 20 hours a week on it for months, and then find a company that guarantees a fast construction period (e.g. Viebrockhaus 3 months). Between finding the land (not buying!) and moving in, you can manage 6 months, but that is already very, very tight... We took almost 7 months between "seeing the land on the internet and moving in". Time could have been saved on the construction time, as we had 4.5 months from foundation slab to moving in.

We decided on a prefab house provider in May 2015 - without a plot. The installation appointment is now in July. The company's order situation has increased enormously in these months...

For us, the contract was signed in February 2015, the installation date was at the end of September 2015, and the move-in was at the beginning of February 2016. Thus, almost exactly one year. The plot was not through the provider. The current workload is probably causing bottlenecks in almost all areas.

Thank you very much for the many responses! It becomes absolutely clear that our idea was pure wishful thinking... Nevertheless, we will now start planning, because it is important to know which district it concerns in order to then look for a temporary solution there. And it is indeed better to be on-site when it then enters the "hot phase."