What should I recommend?

A friend of my wife is moving into a home with her partner. The two have a child and it seems more like a community of convenience than a partnership. The two are not married. But back to the story: An old house is bought. The price is 100k below market value because her in-laws are good with the seller. All in 300k, Berlin. The renovation will cost around 200k. Financing: 50k from her savings, 50k from his savings, 100k from his parents, 300k loan