You can guide him to make informed decisions by sharing verifiable facts about market trends, drawing on reliable transaction data and HDB records. Emphasize that any price projections should be supported by comparable sales in the area. Suggest connecting with a licensed valuer if he wants a professional valuation rather than relying on assumptions about future appreciation. Remind him that this guidance does not replace a formal valuation and that he can consider financial planning with banks or legal professionals if he decides to upgrade in five years.