Another great way to earn money from your home office is to sell your skills or knowledge by teaching classes. For instance, if you’re an exercise guru, you might start an exercise class in a large spacious area in your home. People are willing to pay to learn about many fields of knowledge, from cooking and gardening to soap or candle making. Playing a musical instrument, child birthing, dancing, dog training, yoga, and even foreign languages are all great topics for expert classes.
Nothing beats teaching more novice learners about your passion, hobby, or craft as a business idea (that's a common theme here). Explore dozens of DIY portals (such as DIY.org, DIY Network, Instructables and Mahalo) to get business ideas on how to earn a healthy side income just by showing others how to do the things you love. You can also sift through the countless ad-supported YouTube channels that teach just about anything from guitar strumming to 3D printing.
You can potentially make even more money by offering to handle snow removal in the winter. Shoveling snow is often a homeowner's least favorite job, and there are many homeowners who simply cannot handle their own shoveling because of physical limitations. Typically, snow removal companies charge a flat fee for the winter, no matter how many times it snows. You can offer to remove snow a la carte, or you can copy the standard procedure and charge a flat rate. If you already own a snowblower (or can invest in one), this can help you speed up the snow removal process and allow you to take care of multiple neighbors each time it snows. (A snowblower will also save your back muscles!)
If you live near a university, there are likely all sorts of research studies looking for participants. While I was an undergrad at Virginia Tech, I got paid $500 to participate in a 6-week dietary study. The study provided all my meals and paid me, but I had to eat a 5,000 calorie diet of 50% fat for 6 weeks, plus I had multiple muscle biopsies, urine/blood testing, etc.
Publishing is dead; long live the e-reader! Now that anyone can have their work e-published, it is possible for anyone to make a fortune off their writing. The biggest recent example is the 50 Shades of Grey trilogy, but there are many authors taking advantage of the ease of e-publishing. If you love to write and are willing to do your own promotion (and having a blog can really help in that case), writing an e-book is an excellent way to make money at home.
If you have experience as a personal assistant, secretary, admin assistant, or something in a similar field, then becoming an online PA may be a great role for you. Many professionals want someone to help organize their business and personal affairs. Jobs could include sending emails, managing financial affairs, booking flights and arranging day-to-day activities. If you are interested in this line of work there are many PA agencies that are crying out for reliable assistants.