You may not have all the expenses listed below, for example if the tenant pays utilities or if you manage the property yourself. This is just a list of common expenses. It is extremely important that you build out an estimate on your own before you purchase a property. Most of the information can be gotten by calling around or researching expenses in the area.
If you have specialized knowledge in a certain topic, you can put together an online course to teach others. For example, if you have experience in real estate investing, you can create an online course “Real Estate Investing 101”. The benefit of an online course is that once you create the course material, you can sell it to as many people as you want.