I would like to give a house to my son together with a sum of money so that he can carry out necessary work on it. I am concerned that he may not use the money as agreed. Is there a way to require him to do so?

Yes. You may make a gift before a notary that includes both the real property and the money, subject to the condition that the money is used for the work. Failure to fulfil this condition is grounds for revocation of the gift (French Civil Code, Art. 953).