Trump’s real FEC financial disclosures can seemingly be put off until mid-December, allowing him to take part in the early debates.
Here’s an explanation
http://www.washingtonpost.com/blogs/the-fix/wp/2015/06/17/is-donald-trump-really-actually-running-for-president-heres-how-well-know-for-sure/
So basically he can test the waters before putting up any serious cash.