What should be considered when financing or gifting a family home property?

[*]The exemption amount for the gift is 400k for each parent. Depending on the "other financial situation," it may therefore be advisable to transfer the house initially from 100% mom to 50:50 mom/dad. The tax advisor may calculate this if necessary.
[*]If the gift amount is below the exemption threshold, the (local) tax office does not calculate anything. Only if perhaps a second gift or inheritance occurs do they reconsider whether they should charge anything.
[*]The difference between "right of residence" and "usufruct" is important and should be clarified with a professional. For example, who should receive the income if your parents are in a nursing home (and therefore no longer want/can exercise the right of residence)? The lifelong usufruct for each individual parent puts your parents in a status similar to ownership; the right of residence is significantly weaker.
[*]It is important for your parents that the legal situation is notarized. This costs little. But with a well-intentioned and poorly made contract, it can always happen that the parents end up on the street despite the right of residence. (Ok, here I am on thin ice, I have a forced sale in mind, please check).

That was now layman’s half-knowledge. It has already been mentioned that for a few hundred thousand euros, some professional knowledge should be put into the agreements.

Very good points from
It should be added that the gift tax exemption can be used every 10 years.
Perhaps a partial transfer of now 50% and the remaining 50% in 10 years makes sense.
However, note that in case of a possible occurrence of long-term care for the parents, there is a 10-year compulsory portion period.

I don't know why the tax office is always mentioned here. The OP has said several times that the house is not worth 400k€, yes, such a thing can exist. Additionally, it is not known if it belongs to both parents and how old the parents are. It could also be worth over 1 million without gift tax. Therefore, the tax office has nothing to do with gift tax in this case and it is a bad idea to unnecessarily found a GBR, OHG, GmbH, AG, or KG. Notary fees, however, naturally depend on the value. Much more important is whether the financing bank agrees to the change of ownership. The bank will not give up its first rank in the land register, so a right of residence will be entered as a second rank and will be void in case of foreclosure. But is that realistic? Much more important would be a tax advisor to see if it would not be better to buy the house and rent it out to the parents.

I don't know why the tax office is always mentioned here. The original poster has said several times that the house is not worth 400k€, yes, such a thing is possible. Additionally, it is not known whether both parents own it and how old the parents are. It could also be worth over 1 million without gift tax. Therefore, the tax office has nothing to do with gift tax here and founding a GBR, OHG, GmbH, AG or KG unnecessarily is a crazy idea. Notary fees naturally depend on the value. Much more important is whether the financing bank agrees to the change of ownership. They won't give up their first ranking in the land register, therefore a right of residence will be entered as second rank and will lapse in case of foreclosure. But is that realistic? Much more important would be a tax advisor to see if it would not be better to buy the house and rent it to the parents.

We had considered renting out, but we want to keep it as simple as possible. Moreover, we still want to buy our own house, so it could potentially complicate things here…

. Much more important is whether the financing bank agrees to the change of ownership. It will not give up the first rank in the land register, so a right of residence will be registered as second rank and will lapse in case of foreclosure. But is that realistic? Much more important would be a tax advisor to see if it would not be better to buy the house and rent it to the parents.

Do you have to ask the bank in advance? Could they veto it?

We had considered renting, but we want to keep it as simple as possible. Moreover, we still want to buy our own house, so it could possibly be complicated here …

So, you yourselves do not want to move in there, and the parents do not intend to change their living situation there either - so why the ownership transfer now?