ᐅ Construction Planning Phase – When to Start?

My girlfriend (soon to be my wife, and yes, she knows about this ) and I are both employed in the public sector. So far, we don’t have children, but looking ahead, we are thinking about having two, maybe even three. Of course, a little bit depends on the budget, so it’s closely linked to the house itself, aside from the number of rooms... but let’s start from the beginning.

We have already purchased a plot of land. It is located in Fredersdorf (15370), near Berlin (about 30–45 minutes to the city center). The size is 840 sqm (around 9,042 sq ft), and the floor area ratio is supposed to be 0.25... "supposed to be," because looking at nearby properties makes us a bit uncertain. As far as we know, it’s a plot within an established residential area, not a pure building site. The plot is developer-free. The purchase price was €85,000, although the official land value is €70 per sqm (about 6.50 per sq ft). Accordingly, the financing looks like this: a €59,000 mortgage, €1,000 personal capital, and a €25,000 private loan with the option of early repayment. Please don't start with any parental advice right now. We know what we’re doing. That’s why I’m mentioning the "early repayment option.” Also, the price was high in our opinion but justified and, most importantly, affordable. The plot was previously used as a weekend retreat. On it stands a well-maintained bungalow of 30 sqm (about 323 sq ft) with a partial basement and another 30 sqm... a closed porch? Conservatory? Hallway-like addition with the character of a conservatory??? It’s hard to describe. In any case, it’s dry, wind-protected, uninsulated, locked, and tiled. The bungalow itself is insulated and has double-glazed windows. Definitely not a standard East German bungalow in my view. The bungalow is located in the front third of the plot. Wastewater is connected at the bungalow, and the drinking water connection is currently in the commissioning phase. Electricity and telephone are, of course, already available. Gas is only connected at the street side.

Regarding the plot itself, it is diverse in terms of plants and well maintained. Fence, hedges, pond... the whole package is present. The plot dimensions are roughly 18 m x 47 m (59 ft x 154 ft).

Now to the main point. I’d like to know how you assess where our project might be headed and whether it matches our (desired) expectations. Wishes in such matters are often a negative indicator, so I believe that the opinion of uninvolved third parties with experience can help.

I’m trying to give as much insight as possible. Please don’t complain immediately if I forget something; I will add it later if I can.

We are both securely employed in the public service (no, not civil servants, just regular employees). Our combined net income is €3,700 (about $4,000) monthly. In the short term, we expect this to increase to €4,000 (about $4,300). Currently, we pay €400 (about $430) monthly for the land – we aim to repay this as quickly as possible. Each of us can currently set aside €600–700 (about $650–750) monthly. The planned monthly payment later should be around €1,000–1,200 (about $1,075–1,290) plus additional costs.

Regarding the house and our preferences: We want to build a townhouse-style villa with 120–130 sqm (about 1,290–1,400 sq ft). The buildable footprint CAN be up to 10 x 10 meters (33 x 33 feet), adhering to the boundary building regulations. I will upload a sketch later when it’s technically possible. We want to build with masonry, preferably sand-lime bricks. Our wishes include underfloor heating, a kitchen island, smart home technology, a fireplace, and a walk-in wardrobe, plus a basement. A basement and kitchen island are not absolutely necessary. For self-performed work, possible tasks include basement waterproofing, gas and water installation, electrical work, flooring, and painting, which could be done by family members with relevant skills. Additional costs related to connecting existing utilities on the plot should be manageable. For example, the plan is to take the drinking water connection, currently routed in the bungalow’s basement, back outside behind the water meter and lay it frost-proof at 1.30 m (4 ft 3 in) depth in the rear part of the plot.

Questions:
1. Are there any missing details needed to answer the following questions?
2. Is our project realistic so far, or are we being overly optimistic?
3. What would be a sensible approach to further technical planning?
4. What might be a rough timeline, and what should we generally expect?

Sorry if this sounds a bit choppy at the end; the way I had to write this in stages under the current circumstances is to blame.