Sponsored posts work much in the same way as paid guest posts, but they are posted by big businesses instead of individual bloggers. Therefore, the scope for fees is much higher, as businesses have larger marketing budgets than humble bloggers. Having sponsored posts by large companies will also help promote your site as reputable and as a leader in its field.
I have been making money online for over a year now. Not in the big time yet, still consider myself to be learning my craft. I was doing it really ineffectively (using adsense and amazon along with a t shirt affiliate deal) and driving traffic almost exclusively though facebook. Probably averaged about $800 a month over the last year, mostly because Christmas brought an absolute ton of t shirt sales)
Research individual companies in your desired niche: If possible, it’s always better to become an affiliate directly with a company (if they have an internal affiliate program), as no one else will be dipping into your commission rate. This is the preferred route for most of the prominent affiliate marketers, including Pat Flynn. Unfortunately, it’s also the most work, as you’ll have to do the research yourself to see who offers programs (they’re usually listed in the website footer).