Where to find mathematical modeling help on low-budget project? (Not sure how to formulate this question and also didn't find any suitable tags.)
Are there any online sites where one can find professionals who do mathematical modeling, analyzing data and so on? More general, where to turn if you need help modeling some data on a (low budget) project?
 A: Not sure if you're a non-profit or not, but Jake Porway has been working on launching a Data Without Borders project, where folks can help out on non-profit projects in need of data analysis skills:

Data Without Borders seeks to match non-profits in need of data
  analysis with freelance and pro bono data scientists who can work to
  help them with data collection, analysis, visualization, or decision
  support.

A: You might go to linkedin.com and join some groups that match your needs and ask this question. Alternatively you might approach statistical software developers to see if they could help. 
A: Graduate students. Graduate students, as much as I hate to say this (being one) can be bribed with paper authorships and the like in lieu of actual money. It's important to recognize that said project may get done a little more slowly, as it won't be their first priority if they're also doing something for funding.
Some academic departments also have consulting classes to teach their students future skills needed to be, well, consultants, or practical experience requirements that mean students may be looking for projects. There's also always the possibility of framing your project as a potential masters thesis or the like.
So lots of ways to potentially get free/cheap labor from graduate students. The best place to start is probably emailing the department secretaries of departments from Universities near you with the kind of student you're looking for.
