Complex sentence: James offers Georgy a legal contract, the terms of which are that he would supply her with the luxuries of life in return for her becoming his mistress, and would provide for any "fruit of the union".
Split into simpler sentences: James offers Georgy a legal contract, the terms of which are that he would supply her with the luxuries of life in return for her becoming his mistress. He would also provide for any "fruit of the union".