One of the cheapest ways that a business can be started with is if you already have a marketable skill or you can learn one. Design is one of those things that if you have a computer, software and internet connection you are in business.
You also don’t have to operate a service business to deal with clients you can start a more passive business whereby your designs are sold and you get a commission each time. This can also be operated as a sideline business. Here are some business opportunities in this space: