If I just choose number 2. Just leave our investment there and take him back when the time comes as you said. At least this is wiser in investing and we can relax and enjoy life and the available funds are sufficient to recharge our bodies which feel tired due to full activity.
Are we going to dedicate our time to making money for the rest of our lives?
If you are afraid to take risks of investing that money, keeping $15,000 will be a wise decision. But if you just keep it, it means you don't invest that money. If you want to invest that money, you must choose the option of number 1. Both have the advantage and disadvantage, it depends on us to choose which option that is suitable with our condition. IMO, if we have no proper capability in investment sector, it will be too risky to invest $15,000. But if we know well how to invest in a certain thing and we are pretty sure to gain profits, investing $15,000 should be an interesting way.
However choosing option 1 is not easy and might result in an unexpected result. Investing in smaller businesses, or other people's businesses means that you're not the one holding your money to run the business. This option also shows OP making a rush decision where he can make a quick profit. The best option is to invest money in Bitcoin or if he does not consider investing in crypto, he can save more money until he makes enough money for his planned business.