The mistakes you have mentioned above are really common and mostly beginners made these kind of mistakes. But really appreciate your effort to elaborate these mistakes and to tell how to avoid these type of things. I have also watched many live examples for your point #7 that people spend many of there time for thinking what is good for them, what should they do know, what should be the working plan, what should be the plan of action but they did not implement these things in their business. These thinking and planning is just a time waste if you are not going to implement them.
Carpets make your home warm and cozy. But they also tend to gather dust, grime, stains, allergens and bugs over time. You can tap into this opportunity by launching a carpet cleaning side business idea or serving as an independent contract cleaner in your free time. Either way, you’ll need to invest in proper equipment such as vacuum cleaners, carpet brushes, and cleaning chemicals in order to launch this business idea. Look into the possibility of renting equipment for a full weekend and lining up 5-10 clients to service, to offset your rental costs. If you turn a healthy profit, you'll eventually be able to invest in owning your own equipment and increase your margins, thus going from side hustle to serious business.
You want to stick to the instrument(s) you know, but you may be a skilled enough musician to offer lessons on several different instruments, or those in a particular class, e.g., stringed or woodwind.You can decide to take on individuals or classes, depending on space and availability of instruments. Public schools are continually reducing their commitment to art and music classes for students, so you can try to work with the public school system to supplement their efforts in those areas.
Your job, in the case of rental units, will be to make sure the property is running smoothly. For seasonal properties, you will most likely spend your management time making sure the property is ready for seasonal visits and well-maintained when no one is around. If the owners go away for six weeks in the winter, the property manager makes regular checks on the property. You will be the contact number if the security system operator needs to contact someone about a breach in security.
Starting a business in this field will require some experience, but as long as there is anxiety, there will be a market for coaching people to create and deliver presentations. Invest in video equipment or use a smartphone to record students as part of the coaching process. If you have a background in radio or TV or specific experience in high-profile public speaking, all the better.
Market your talents to building contractors. People purchasing new homes can often be overwhelmed with the choices and possibilities in home decorating. Design some questionnaires for each major element and each major room in the house. Find out how the homeowner will use the home--are there children? Pets? Does the woman of the house wear high heels? Do the home's residents neglect to remove shoes? How will each room be used? Where might task lighting and ambient lighting be most appropriate?