I've read on blogs that it's important to have a contract that is read and signed by both parties involved in the transaction.

Does one have to have a lawyer in order to create a business contract? If so, what type of lawyer would create one? Corporate lawyer?

If the buyer is in Canada and the seller is in the US (or vice versa), does this have any implications on the legal validity of the contract? Should there be a certain type of contract used depending on whether the transaction is international or national?