I have an idea for a new product and I want to hire a CEO, who will
lead this project. We have set 3 milestones, which he will be
responsible on and evaluated on at the first stage. On each milestone
he will receive more portion of the future company:
Milestone #1: Signing on contract - will receive 5%
Milestone #2: Fund Raising - will receive another 5% (Total 10%) 
Milestone #3: Establishing a company - will receive another 15% (Total 25%).
What other issues should I insert to the contract?
For example, what will happen if he will not be able to raise the
money, or what will happen with his share if he will leave the company
after the second milestone?
Where can I find a sample contract?
Thanks.

Just a personal comment, 

I would suggest that you are going about this the wrong way.  If you
are serious about your product, you should create a business plan,
then found a company.  At that point once you have a plan and a
company you can talk to a lawyer about bringing on a CEO for that
company.  Assuming that the person has any expierience founding and
running companies, he is going to want a contract that has been
reviewed by lawers and you are going to want a lawer to represent you.

As an additional comment, as someone who has founded a compay with a
friend without consulting a lawer, I can not stress enough how it is a
huge HUGE mistake to try to create a company without having all
documents reviewed by a lawer.

You should probably see if there is a small business center in your
area that can help you get started.....

I totally support "vballguy-ga"'s comment. 

As a golden business rule, you should put in charge a person who is
really determined and passionate about your business. And this should
be you, as the one with the first initiative

Also, staying as the main initiator of the business will be a good
exit plan in case the CEO fails.

I suggest you also read the following articles on the web:

http://www.thecorporatelibrary.com/companies/g/gblx/ceo_gblx.htm - A
CEO contract example between GLOBAL CROSSING LTD. the company's CEO,
ROBERT ANNUNZIATA

http://sify.com/news/internet/fullstory.php?id=13219394 - a nice and
detailed interview with a CEO and about his starting of a new company
in IT.

http://www.fastcompany.com/resources/columnists/mg/050304.html - from
the well-know Fast Company, an article entitled "The CEO of the 21st
Century".