So simple as that, selling out would mean changing who you're. Sponsorships are nice, but try not to sell it out, keep the same attitude throughout as stated. For as you risk losing a good number of your audience when they read, your contents, blog/view it.
I believe, this will help you have quality blog. As usual, if you think, this was useful to you, share with someone, with friends and families. Feel free to ask me questions in the comment box below Cheers.