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.
Depending on your skill set, you could easily make a few hundred dollars or even a few extra thousand per month. And if you have some money to invest, you could easily launch into a variety of day trading activities. Those present some risks of your original capital. But if you know what you're doing and you work to hedge your bets by placing stops and limits, you could create sizable upside with lower-than-usual risks.