Be very picky about who you hire. The quality of your employees can make or break you. Hire people that you trust to run the business in your absence, so you can take a break once in a while. If you understand how capitalism and the free market works, you should do well
I've heard that around 30% is a good number for rent. I pay close to 50%, however. My suggestion would be to move to the bad part of town and buy a gun