House construction project with terrible credit rating and almost zero equity capital :-)

Unfortunately, the OP leaves the questions unanswered. Depending on where he lives, you can't even get a plot of land for 400k. Land plus new construction plus additional costs will almost certainly not be feasible. Looking for an existing property is a good tip, in my opinion. If you are handy as stated, you can certainly make something nice out of it. I think some people are attacking you here because it’s not entirely clear from your initial post whether these are your own children with disabilities (which is how I interpret the care level) or foster children.

He can’t afford it. Especially since nursing care benefits are not considered sustainable by the bank. Period.

It's a pity that many people here immediately think of an afternoon show on RTL when they hear "5 children." I also have 4 siblings and my father was the sole earner until a few years ago (when some of us had already moved out), thanks to a home loan (existing property!) vacations were only possible every few years and yes, my parents had to refuse many wishes (including hobbies) for cost reasons. I also shared a room with one of my sisters until shortly before I turned 18, but I was always happy and it didn't harm my relationship with my parents or siblings, and actually, something has come of us kids.... @TE look for existing properties, as everyone here says, and they don't necessarily have to be huge, but maybe there is a bargain (once your finances are healthier again).

That's pretty harsh stuff some users are posting here. Absolutely terrible. Most of these posts wouldn't have been said in a personal conversation with the OP. I'm sure of that. I am at a loss for words regarding this behavior here. I don't usually see this here. Here is a person who has probably suffered more than one blow of fate. Trying to provide a better life for their family, and here people say they should try contraception?

My opinion is that you are taking on too much with building. In my opinion, even an existing house is a waste of money. Think about it - you need 6 rooms. And what happens later? They will all stand empty. Your budget is not the worst but still limited, and unnecessarily going into debt for that? Stay with renting. Try to get a house through other means than the usual ones. In 10-15 years, building a house is still interesting when the first kids have left the house.

It's a pity that many here apparently think of a typical afternoon family on RTL when hearing about 5 children.
I also have 4 siblings, and my father was the sole earner until a few years ago (when some of us had already moved out). Thanks to the mortgage (existing property!), vacations were only possible every few years, and yes, for some wishes (including hobbies), my parents had to say no for cost reasons. I also shared a room with one of my sisters until shortly before I became an adult, but I was always content, and it didn’t harm the relationship with my parents or siblings, and in fact, something has come of us children...
@TE look for existing properties, as everyone here says, and they don’t necessarily have to be huge, but maybe there’s a bargain (once your finances have improved again.)

I’m also from a family with 4 children, no vacations, father was a laborer. We lived in a rented house. Sorry, the income just doesn’t match the desire. Period.

Some pretty harsh stuff that certain users are letting out here. Under the belt. Most of the posts wouldn’t have been said in a personal conversation with the OP. I’m sure of that.

My goodness, just calm down. People like the thread creator come to the forum precisely because of the anonymity and especially because it’s not a personal conversation. The thread creator consciously did not ask the house bank, a broker, friends, or colleagues, but us here. Voluntarily and fully aware of their situation.

I’m at a loss for words about this behavior here. I’m not used to that at all here. There’s a person who has probably suffered more than one stroke of fate. Trying to provide a better life for their family, and here they’re told to try contraception?

Well, the OP has dismissed their own debts and those of his wife as youthful indiscretions. That implies to me, in a completely neutral way, that it was not a stroke of fate, but self-inflicted. The only real stroke of fate is the need for care, but apparently they are managing that very well, the care level is even decreasing.

Most of the “mean” comments probably arise from the misunderstanding that unrelated children were taken into the family as foster children. Obviously, that is not the case. That was just awkwardly expressed in the opening post. These are not foster children, but their own children who require care.

What many here find strange is that there is still such a high savings rate. Because if care allowance is already being paid, I would first assume that the children actually require higher care expenses. I only know it like this: that the subsidies never seem to be enough. Instead, a lot of money remains. And then the father even has time during vacation for internships in craft businesses? Aha. No offense intended, but the situation is quite unusual and portrayed rather glossed over.

Anyway, there were also good tips here regarding buying property aside from new builds.

It's really wonderful how some people can get so outraged... first of all, the OP is responsible for their own situation. I also can't see any misfortune here, just a huge pile of self-made problems and daydreams.