With regards to laundromats, they are def not passive. We researched them for almost a year before deciding that they were not for us. They need to be run like a true business. First, you need to have employees - these are usually low-paid workers (read: don't show up on time, call in sick, or quit). You also need to have a way to repair your machinery - depending on the age of the equipment this could get costly if hired out, or a royal pain if you're skilled enough to do it yourself. You also need to keep the quarter machine full (or install expensive card-readers). Also, your customer base is static. Meaning, that no matter how 'good' you run your business, people are only going to travel in a small radius to do their laundry. You are often competing on price with other mats, and not service. In addition, you have no control over price increases in your utilities which are your major variable expense and incredibly hard to pass on to the customer. Oh, and according to the laundromat forums, vandalism and theft are very real and occuring incidents - many old timers carry guns when collecting their monies.
The upside is that it is a cash business - the downside is that when buying a business, it's very hard to confirm the income the owner is claiming. One non-traditional situation that might work for someone is if they owned the building that the mat was in and lived in the apt upstairs - that type of set-up could possibly work and lend itself to a mustachian way of life.
