I have an account in a pretty specific health-related niche. It's not that large of an account, but not that bad: in the 10k to 20k range. I'd like to sell tweets to some companies that would be interested in this audience. A few questions: -What would be a reasonable price to charge? -How many sponsored tweets could I do without annoying my followers? -Would selling tweets create any problems with my account, as long as it's disclosed? -Why is it that when some people sell tweets, they delete those tweets a short time later, like after 30 minutes?