How many square meters are realistic given the following financial situation?

50,000 - 60,000 euros of own contribution is a tough nut to crack.

Especially if you consider the addition from the architect:

(even with little knowledge)

I consider that simple whitewashing.

We helped with the installation of the controlled residential ventilation (among other things, laying pipes in raw ceilings), pulled all the network cables ourselves, installed the underfloor heating ourselves, and will lay the floors ourselves. We have by no means saved 50,000 euros...

So our house is just under 120sqm, but we are saving just under €30,000 with complete drywall construction inside (plus boarding / painting etc.) and laying all the floors (except the main bathroom) with EL. And it's going to be absolutely hardcore, we're not kidding ourselves - so I really don't know where about €60,000 could be saved with amateur DIY work.

just for comparison (I have already written this in one place or another)

In total, we are building 300m² of living space (2 semi-detached houses). For this, we are doing all the drywall work (but not the spackling, that we outsourced). The ceiling underside + insulation + foil for the upper floor + attic, laying all cables (several kilometers of NYM, SAT, CAT.7a (for LAN + smart home) in protective conduits and connecting them at the fire points / switches, 24V low-voltage wiring in the distribution cabinet for smart home, controlled residential ventilation from a total of 8 air distributors for 16 connected rooms, all pre-wall elements / boxed-in sections, all floor coverings (partly real wood, vinyl, tiles in 4 bathrooms) + "construction management / organization", installing interior doors + technical room doors and much more. It might have cost 50K if outsourced, but I don’t really believe that ... and often it’s been 2 - 6 of us who have spent almost every weekend since the shell construction (Friday afternoons + entire Saturdays) + many, many afternoons on the construction site.

And we are far from finished; until the end of August, I still see several hundred working hours flowing into the house.

And I won’t even mention frills like the development of a "custom" GUI and a dynamic connection plan for "our" smart home system.

Many of the things that are called do-it-yourself today were simply done in the past without mentioning them, and pricing them into equity was out of the question (I mean wallpapering and painting, which today can quickly amount to several 10K because of all the perfectionism we "impose" on ourselves in the age of industrialization at the end-customer level).

Thanks for the quick responses!

50,000 - 60,000 euros of personal contribution is a lot

Yes, that's exactly what we thought too. In the conversation it sounded so "normal" that we agreed right away. Of course, we already have one or two ideas where we can and definitely want to do something ourselves, but I'm pretty sure we can't save the mentioned amount that way.

And what was actually "ordered?" The 500k€ option?

We agreed that the upper limit "can" be at 500k€.
She is, of course, trying to stay below that. In the end, she is now trying to realize our wishes within 450k€ - 500k€.

My God, those are just numbers. Unbelievable.
You just have to get used to that first.

Attention, be careful. In construction, people quickly talk about extras or so-called "small things" that usually cost at least 500€, more like 1K - 5K. That adds up. And if the architect is given a 500K budget, in practice it tends to be more like 600K. And you usually don’t have a 100K buffer just lying around.

Attention, be careful. During construction, people quickly talk about extras or so-called "little things" that usually cost at least 500€, rather 1K - 5K. That adds up. And if the architect is given a 500K budget, in practice it will be more like 600K. And you usually don't just have 100K buffer lying around.

Ok!

I find that quite a "strong" statement.

Our architect is an acquaintance. She accompanied two friends until the building application and upon inquiry, both ended up roughly where she had given the cost estimate beforehand.
But of course, you yourself are involved in deciding which fittings you choose.