Hello,
as already mentioned, building without equity is quite expensive. Although interest rates have risen in recent weeks and months, we are still at a historically low level. As long as you get a rate acceptable to you, you should go ahead and build. While you can secure a nominally low interest rate for the future through a [Bausparvertrag], since no [Bausparvertrag] has been concluded yet, you would have to bridge finance the [Bausparvertrag], which is comparatively expensive. If you still conclude a [Bausparvertrag], pay close attention to the repayment rate. In the repayment phase, there will be high burdens. 5-7% are not uncommon. Since no equity is available, you will have to finance not only various additional costs but also the completion fee of the [Bausparvertrag]. In the effective interest rate calculation, the completion fee is left out, at least it used to be that way. It is assumed that you pay it in cash. Although there is the nice state [Riester-Zulage] of 154.00 per person, you can quite simply calculate how many annual allowances are needed to recoup the completion fee. A tax-advantaged and consumer-friendly option is the [Riesterannuitätendarlehen]. Apart from some restrictions regarding the property (e.g., no rental), your repayment payments are special expenses in the tax return in this case. The state [Riester-Zulage] is from the start a free special repayment by the state. As with all [Riesterprodukte], taxation applies in the pension phase. Provided one reaches a taxable amount. If the house is intended for old age and the tax payment can be made at once, there is apparently still a tax discount of 30%. Unfortunately, this [Riester]-product is rarely if ever offered (you really have to ask specifically). The bank earns nothing on it besides interest and a modest account management fee for issuing the allowance certificate. For you, these are special expenses and state special repayments. And more repayments mean less interest income for the bank. In addition to the obligatory special repayment right of 5%, one or the other free repayment change is also possible. This way, you can considerably reduce the loan after the fixed interest period to a healthy level. If your company develops well, that is possible. If not, you still have to pay interest + 1% repayment anyway. You have to weigh that personally, use a repayment calculator, calculate various options, ask the tax advisor, and then decide. You have to make these considerations yourself. No bank will do that for you. In this case, I also know what I’m talking about. Within a 25 km radius of my place of residence, I have talked and negotiated with 20 banks. I aborted one or another "consultation" and expressed that I did not perceive 19 "offers" as such politely. Ultimately, one bank followed my arguments. But you don’t need more than one anyway.
Good luck with the banks and possible house building!