Build new or buy old??

Hello everyone,

For 2 years, there was nothing suitable that was interesting to buy.
Now there are two properties in 89231 Neu-Ulm. Help!
What would you tend to choose if both would suit you well, to buy an old house or to build new?

Brief details.
Old house: Built in 1967, bathroom renovated 10 years ago, balcony, terrace, semi-detached house, 5.5 rooms, 139 sqm + expandable attic (nothing has been done here), total area with garden 465 sqm, garage with electric door, very very quiet location, district, available immediately, oil heating (technology, guest WC (so far without sink), pressure equalization tank, etc. was renovated a few years ago, so it is relatively new), central heating, energy demand class G-H. All wallpapers and carpets would have to be removed, new flooring laid and walls papered/painted. Half-turned stairs everywhere, to the basement and attic without railing.
Purchase by bidding process - highest bidder gets it. (Inheritance community wants money). Minimum bid: €300,000
We have roughly calculated flooring and painting work, as well as remodeling of WC, tearing down wall in living room, installing new kitchen, totals about €370,000.

New house:
New build within a building community with 7 parties, terraced house with solid carport, total area 214 sqm, 115 sqm and 4 rooms (3 rooms upstairs, 1 office with light well in basement which could be counted with about 12 sqm added to the 115), underfloor heating, guest WC, terrace, flat roof (cube design), I-stairs, KFW 55.
Cost for everything, ready to move in spring 2017: €400,000

Who can tell me what I should consider for each property?
Financially we are at the top limit with €400,000.

Energy demand class G-H <-> You would have to tear out all the wallpaper and carpets and lay new flooring and wallpaper/paint. Half-spiral stairs everywhere, to the basement and attic without railings.

That doesn't make much sense already. What exactly do you want to do about the relatively high additional costs?
Personally, I would rather advise an existing property, but it also has to fit and be financially manageable. With the energy demand (=additional costs) and the associated purchase price, I would probably keep looking.... or be able and willing to carry out the renovation. If not, then it doesn't work. Searching for 2 years is not unusual ;)

Supposedly, two people in the house consume 2000 liters of oil per year according to the broker, there is an 8-liter tank inside, which is still half full. The solid wood windows and walls are very good, he also said, and insulation is not worthwhile here.

1967: in need of renovation! New electrical system, insulation... G-H -> high energy costs.

2017: are all costs really included in the 400000? What about higher-quality fittings?

Yes, that seems to be a good seller ;-P So get an expert opinion (=appraiser) and then you will know more - especially with a house from the 60s (possibly hazardous substances & co)

In new construction, it is said that you typically calculate with 3000 € / m². However, you are probably somewhat below that, says the architect, because you can still choose everything regarding the craftsmen (it is put out to tender and decided together) and of course you can also choose low-cost tiles / flooring / faucets, etc.