YES!! That is how ALL businesses operate. They buy items at a "wholesale" price (discounted) and sell at a "retail" price which is what you have to pay when you take it off the shelf. That's how profit is made in brick-and-mortar stores. Online selling is the same except you don't have huge overhead costs (rent, employees, etc.) to cover. This gives you an advantage of being able to keep prices reasonable and garner more customers and repeat business.
Working from home is the direction that the job trends are going in and is growing popularity with families that don't want to have both parents working out of the house while strangers raise their kids. It's also a bonus cuz you set your own hours and are not limited by your location. Smart you :-)
Just remember: Be fair, treat your customers right and make a good name for yourself.