It appears from the original post that the OP is unemployed. Interest income of €200 per week would not give rise to significant or perhaps any tax liability.
The return of €200k at the end of the period would have no tax implication as the repayment of a loan.
Thanks all for your input and @cremeegg's friend, it's a nice idea and I wish you well I will carry on with my research before I decide what to do. Thanks again.
If you mean, do I seriously expect the OP to lend €200k to an anonymous poster to buy a house, then no I don't, and I wouldn't do so myself.
However, although I wrote the post myself, FO'C represents a real person and their circumstances. I wanted to see what flaws other posters might see in the proposal.