A business that caters to people who want someone to take care of their pets during the day when they are at work or vacationing.  A drop off in the morning and pickup in the evening or anytime during the day type operation.  Recruit others to be part of your business and run operations from their own homes nationwide.  Hire people as independent contractors initially.  Start in one location and work out the bugs.  Expand to other locations as the business grows.

Make and sell home made dog treats.  Benefit from a huge profit margin and the willingness of pet owners to pay higher prices to give their pets a good treat.
 

SUGGESTION:  Start with recruiting pet owners in your neighborhood or friends and family with pets as your client base.  Expand your client base by promoting your business to Veterinarians.  Expand the business by recruiting and training others to make treats with your recipie.  Expand to other locations as the business grows.. 

If you like pets and enjoy the medical profession how about starting a Vetenarian practice.  Like human beings pets also need medical attention.  Pet owners pay tens of millions of dollars each year on pet care.  You will require to have a doctor's degree in Vetenarian.  In addition to a decent size office you will need medical instruments, medicines and other medical supplies, as well as a small staff to get started.