Pick the most boring businesses around and you will find the money. Don't try to get cute, just provide good service and fair, not cheap, prices in an area with traffic and you can't go wrong. Dry cleaners, convenience stores, repair services, auto shops, etc...those will make solid incomes no matter where you locate them and you certainly don't need to be creative with them.
One of the best businesses around which has very low start up costs is repairing appliances. You get to charge $60-90/hour in labor plus 20-50% markup on parts. You pay your repairman $30/hour and run the business with a cell phone from your garage or in a cheap shop in the low-rent district of town. You can easily scale the business based on demand. You can even start out by doing the business "off" hours. Find a guy who is already doing the job 9 to 5 and ask him to work for you on an on-call basis after his regular job. Put in your ads that you specialize in evening or weekend calls, but of course charge a premium for that. You will have little competition for this niche and you can always find one of these guys that needs the extra cash to moonlight for you. Once you have enough business, you can do it full-time and get some dedicated daytime staff. I would love to get back into the business, but have my hands full with work already. I did some of the logistics work for this with a friend some time ago, but he left the country. While running it this was a great cash cow, very little work effort needed and done properly it created a nice tax shelter.