Depends heavily on your financial freedom state. And other factor is the post itself. The sponsored post must be of high quality and at least fact based.  Factors like audience size, engagement, niche, and how much audiences value their authenticity are important. 
Otherwise your audience will have drop or have the feeling of being betrayed or sold out. It also should be clarified that it is a sponsored post.
 But in general and for an averaged typical content creators, a common balance is 1-2 sponsored posts per month—enough to monetize without overwhelming followers or risking trust. Too many (5+), and it might feel like a sellout