We (both in our mid-twenties) are currently building and hadn’t saved any equity either. But due to the low interest rates, we thought, "Let's see if the banks go along with it." Our realtor recommended an independent financial advisor, who immediately said it would be difficult without equity. However, my house bank (Sparkasse) agreed and even financed the additional purchase costs (which is a must without equity, and according to the recommended advisor, most banks would have dropped out at that point at the latest). The important thing is that the house is in a good location. Then you might be able to sell it off more easily in the short term if unemployment actually occurs or something similar. Even then, you will certainly make a loss, but you don’t necessarily have to end up with Peter Zwegat right away.
One should be aware that building a house is always a risk. However, here (the Stuttgart metropolitan area), existing properties also go for a fortune. Therefore, in our price range, it doesn't really make much difference whether you build something mediocre or buy a reasonably well-maintained existing house. Cheap here only means garden plots, houses without public transport connections, or renovation cases.
A household budget book is – as already said here – the be-all and end-all to get an overview of expenses at all – you always forget something when calculating quickly. For example, our washing machine broke two weeks ago and needed replacement, which also had to move into the house – so something better, and high three-digit sums just disappeared "just like that." Such things should ideally also be recorded in the household budget book so you know whether you can still afford the installments. We have had a household budget book for over a year now, and slowly I can reasonably estimate what we need each month for the different areas.
Even if no equity is available, one should be able to save some. My predecessor also seems to doubt this with the statement "37/32, both employed and without equity, that would make me think..." He is right in that you should always have some reserves. Whether you throw them into the house or not is, in my opinion, not so decisive. On the contrary, if you use them as equity for financing, the money is gone initially, and you can’t make emergency purchases with it. We have made it a goal to save a lot and now already have equity – but we do not use it for the house, rather as a reserve for things like washing machine, car (the house is a bit outside, and then it becomes at least necessary to get a car for convenience reasons), or occasionally a vacation. Here, too, the household budget book really helped us. After the rather pessimistic initial estimates, we were even able to increase the savings rate in recent months. The money is parked in a free daily allowance account of a German bank. That way, it is reasonably safe, and you don’t constantly see the sum on your current account (which could perhaps tempt you to just spend the money). And as long as negative interest is not yet charged on deposits, it is still somewhat worthwhile. Finanztest often publishes reports on current reputable daily allowance offers with (comparatively!) high interest rates.