The fastest way to make money is to give the public what it wants. Give the people what they need and you will be booked up for months. And sometimes what the people need the most is to have help with home decorating. Lots of people need help getting their homes spruced up. They do not have time to paint and hang wallpaper themselves and if they did they would not want to. It is much easier to pay someone like you to do it for them.
If you want to get started in the wallpaper hanging business, all you need to do is tell a real estate agent that you are available. They can help you get the first jobs and the rest will be referrals from your customers. How many people do you know that want to spend their weekend hanging wallpaper? None, right? That is exactly why they will be willing to pay you for the job. That makes this the fastest way to make money, and how much money you decide to make is strictly up to you. How fast can you hang wallpaper, and how good are you at it?
All you need to get started are your papering supplies; if you have done much papering you know that all paperhangers have their favorite tools.