1. No minimum number of VOTES. In theory, 1 Up Vote from a 99 REP member might be enough (in practice more like 3-5 minimum). In practice there have certainly been posts with over 1,000 Up Votes that did not payout (lots of 0 REP Sybils or Bots).
2. It looks like you found the White Paper, but be aware that the mechanism is actually a cool bonding curve formula. See Below For More Info.
General Vote/Payout Info
Number of votes is NOT the same as rating (hover over the vote count on desktop to see the score). A post could have 1,000 0 REP members up vote it and it still be very low scoring or 5 99 REP members up vote it and be very high scoring. All votes are not equal.
Beyond that, timing, amount bet, and bet location matter. Earlier bets, larger bets, larger proportions of bets, and communities with more bets matter.
Even beyond all of that, if a post is not above the 50th percentile on relevance (no matter how many up votes or how much staked on it), the payout will ALWAYS be 0.
All of this information is already available on the platform, though I do not know if it is all directly spelled out in the same place. In the white paper you can get the rough idea and several of the blog posts spell out the mathematics and mechanics in more detail.
The amount of shares you get for each bet is determined by this formula:
yourShares = 1/2 * (currentBets + yourBet) ^2 - currentShares
So to get the 1st share you would need to stake .5 tokens. 2nd share would be more 'expensive' and require 1.5, 3rd share would require 2.5, and so on.
The payout is split among all share holders of the post based on how many shares they hold.
Each additional person to stake will both dilute the rewards pool and add to it, though the later they are in staking the more ‘expensive’ a share, so the more they will have to pay for a comparable stake. They may also make the pool much more likely to pay out depending on their REP.
Choose wisely how you deploy your bets as you will need to bet on good, relevant, content in order for the payout to happen, but by the time you can be certain of a payout, the potential reward will be really small or considerably more expensive