Less capital now than ever. Local service businesses like "Mop It Up" would cost almost nothing to operate. The barrier to entry is simply that the work is undesirable. This makes it valuable.
I don't think your conclusion at the end is true. Most undesirable work is in fact not valuable, in the sense of being paid well or easy to get, because, at least if it's also unskilled, there is a large supply of labor relative to demand. Stuff like janitorial work does not pay well and has no shortage. Similarly with McDonald's: they typically get many more applications than open positions, and not because they're paying $20/hr.
There was a story (I think it was on reddit, not HN) of an entrepreneur who bootstrapped a local cleaning business in something like three months, by hiring his maid as his first employee. The guy does not mop up himself, but runs an incredibly successful business with a web-based reservation system. The rest of his job is people and asset management.
So even with janitorial work, an educated graduate can turn it into a profitable business, without actually doing the cleaning himself.
Edit: his site is http://www.maidsinblack.com/ and he does a great job of documenting his startup experience step by step on reddit. If I find the thread, I'll post it here.
