The site will have 10 participate of which where image will be there..at the end of the competition the person with the highest vote wins but for people to vote they have to use real money...for example 10 vote can be equal to 20 dollar for each dollar added the vote of the person IncreasesHmm.. Sounds more like you are talking about donations/fundraising/crowdfunding, or even betting, rather than voting.
Hard to give any advice without knowing the end goal.