Gifts are just random. Once one of my sims got a gift from a long-dead friend. I think at the time the gifts were spawned that day, his ghost must have been out and about. Another sim got the Fountain of Youth, which costs $500,000. I kept it, and put it in their yard. Their bills were suddenly much bigger, but my sim was an adult when she married, and already very wealthy from making and selling elixirs and selling metals and gems from group science project meteor showers, after cutting and smelting them herself.