1) I own a small rental property in Florida that is fairly low maintenance and pays for the mortgage + a small amount each month on average. This is a long-term ROI play since after taxes, maintenance, repairs, and everything else it ends up being close to a wash until the principal to interest ratio on the mortgage payments improves after 5+ years. I only say this because everyone and their brother in my age group seems to want to retire on rental properties, but in reality it's really not that great.
2) Basic ETF investing in a combination of value-oriented and dividend-oriented ETFs. This is, in my opinion, the only way to get truly passive income with literally zero ongoing effort.
3) I design and 3D print props and cosplay pieces on a referral basis for commission. In reality it's a horrible way to make money since quality 3D modelling for 3D printing is time consuming to the point of the hourly effective rate being lower than minimum wage, but I enjoy it, so it's kind of a semi-paid hobby.