Learn then selling guidelines. Each marketplace has guidelines that define what you can and cannot sell. State and federal laws also impact what items are prohibited. In general, you cannot sell alcohol, weapons, service contracts, animals or event tickets. Also, while not always prohibited, you may find restrictions on how you can sell items in some categories, such as art, gift cards and coupons. eBay, Craigslist and Amazon publish these guidelines on their websites.
Again, if your blog has a large reader base, then businesses may be interested in paying you to review their services or products. Not only will you get a free trial using whatever these businesses are selling, but you will also get a fee for writing them a review and posting it to your site. Paid reviews (and other paid and sponsored content) can be big money, so advertise this service on your contact page to generate business.