There are many websites that offer so-called "contracts" that people think they can use for their, often "unique" situations. However, while many persons seem to think that words on paper (contracts) are nothing more then "cut-and"pasted" by lawyers, that is not accurate. For example, you say you are "putting coin operated rides in retail stores" - to an attorney that may immediately indicate that any "contracts" between the ride installer and the retail store should include terms regarding the following (at the least):
Who owns the rides?
Who is responsible for any harm done to the rides?
Who must repair the rides if they break down?
Must notice be provided to anyone if a ride breaks, harms someone, etc.?
Who must pay for a ride if it is stolen?
Who is responsible for any harm caused to a user of the rides?
Who will pay for the lawyers if either the store or the ride operator is sued?
Should insurance be provided for the rides and by whom?
When, exactly, is payment do and how should the contract be written so that payment as desired is really enforceable?
Should arbiration or mediation be used instead of courts?
Can interest be charged on late fees?
Can the rides just be taken out if payment is not made?
And on, and on ...
While there are "contracts" available on the internet in various websites (just typing "contract" into Google or Yahoo produces lots of sources or examples) those are "generic" agreements that may or may not properly protect your business interests. It is always best to meet with an attorney who is familiar with contract work and who can design a contract that is specific to individual needs. For example, my contracts professor told my first year law school class that simply the misplacement of a comma can lead to a result which the parties to a contract had never anticipated. This may seem ridiculous, but, in reality, the placement of a comma in a sentence can change the meaning of a contract and, therefore, the responsibilities of parties who sign that contract can be changed simple because a comma was put in the wrong place (this is one of the reasons why attorneys need to carefully consider the words they use and, if they feel they need to, define terms for the contract to be sure a meaning is clear).
For this reason, you should really consider hiring an attorney in your state, whom you feel comfortable with, so he or she can review your business, your potential clients, and then prepare a contract so that your interests are protected as much as possible. If you can, you may even want to seek a referral from business persons, friends, or families you know about attorneys they have worked with.