Lets assume you put the max of 5000 per year in a ROTHRoth IRA. You have your home and all other debt paid off, and your investment earns 10%, a few points below the market average. You will have $822,470 at 65, 1005K at 67 that you can draw on tax free. It is a fairly tidy sum and should keep you from working as the greeter in WalMart.
This kind of return should be expected from most mutual funds, and you could invest some time in reading about how to pick good returning funds. An index fund, which shadows a market index, should have that kind of return. And yes that is 10% per year. In investing it is about momentum.
I too write software for a living, and would suggest you should be able to contribute about double that amount and still be comfortable. That would set you up for a pretty comfortable post-work life style.
You understand the value of building passive income. Traditionally that is accomplished through dividends of reliable companies, but are now accomplished a variety of ways.
Keep in mind the way you are asking this question opens you to many scams.