There are many businesses out there that you could start, such a lawn care, or a small handyman business, but if you do not have a large skill base and prefer the indoors to the outdoors then start a cleaning business today.
My wife and myself own a cleaning business and when we first got started we chose to start office cleaning, business was great.  The reason for this was we preferred to work in the evenings and early mornings, giving us our days for other things. 
The number one thing you need when you first start is clients.  And to get clients you have to have persistence and drive.  This normally will come from having a desire to succeed.  If you do not have this desire then turning on the TV or going out with friends will be much too easy.  But with this desire you can push through and build a small cleaning company.  And from there who knows what can happen.  You just have to wake up and get starting cleaning.  Business will come!
If you start your own cleaning business today you could walk away from your regular job in under a year.  Yes, it can really be just that easy.  Imagine you have just 10 clients, each of those 10 clients need your cleaning services once every one to two weeks for 3 hours each.  At $25 per hour that is $25K per year for only about 20 hours of work per week.  And commercial is higher than that, and finding people to help you clean is easier than any other business.  There are many people that would like to work just 5 hours per week. 
Good luck with your new cleaning business!