Financing better with or without Wohn-Riester?

Income tax on Wohn-Riester and giving up owner-occupation Riester savers who give up owner-occupation of the residential property during the accumulation phase or during the pension phase within Wohn-Riester must pay back tax on the outstanding amount of the housing promotion account - at their individual tax rate - as "other income". Such a tax-damaging use occurs if the residential property is sold, rented out, gifted, or transferred free of charge to relatives, or if the Riester saver dies before the age of 85. To avoid hardship cases, the 2009 Annual Tax Act included that the allowance recipient's absence due to illness or care needs does not constitute a tax-damaging use. However, the allowance recipient must remain the owner of the apartment and the apartment must not be made available to any third party - except for the spouse in the case of joint assessment - for use.

...How would you do that?...

All representations are "lagging". The total effort of a financing including all costs is also interesting!

v.g.

Nevertheless, the answers were already helpful. Thank you!