We have been doing criminal background checks for about 15 years. The profit margin is slim indeed. If you live in a metropolitan area you can make a fairly good income with volume doing it for nationwide pre-screening companies. Most counties are not online, but the States have an online service which charge a fee, very slow, and not always updated on a regular basis. Our State charges $10.00, can take up to 2 weeks to get the information back to you. You have to pay it upfront and they will only except mail forms. Some counties only report quarterly, if at all. That leaves a pretty big gap for a person to create a crimnal record.
  Most of the people who need these searches are in a big hurry to hire or rent their property. Therefor, a 24 hour or less turn around is mandatory. 
  It has taken us 15 years to build up a decent client base and put efficient tools to work. Plus the fact we cover several counties in our state. So it isn't a quick money maker. 
  My advise would be to go to your local restaurants, bars and any business that has a high turn over and offer to do their felony/misdemeanor checks for say $10-$12 for each name.
  If you have anymore questions, feel free to contact me.

Good Luck,
Sharon