I agree with Voki1. Don’t count on something that is not yet foreseeable. The statement that nothing stands in the way of a permanent contract is worthless as long as you don’t have it in writing. So you should actually ask yourselves what will happen when the contract expires.
Nevertheless, as Payday already wrote, a fixed-term contract is not necessarily a deal-breaker for banks. I can tell you that despite my fixed-term contract and my husband’s probation period, we got financing without any problems (and would have gotten it from the other banks we inquired with as well). But: 1. For me, a fixed-term contract is typical for the industry. In my current position, there are only fixed-term contracts. 2. The job prospects are good, so that even without a permanent contract I would immediately get a job with equivalent pay. 3. The financing would (at least financially) also be manageable with only my salary. 4. My husband "voluntarily" changed jobs to a higher position with correspondingly better salary. 5. We had an appropriate equity ratio (about 30%). As you can see, it ultimately depends on the overall situation.
Only one thing I strongly advise you: Do not conceal your fixed-term contract from the banks. Otherwise, you risk the loan being called in by the financing bank in case of doubt.