Contracts in Alberta are legally enforceable. First, all contracts regarding property must be in writing in order to be valid. A verbal offer is usually ignored as it is considered a wish - it is not enforceable. This pertains to both rentals and purchases. Verbal offers for things not related to land or housing are valid and might be enforceable.
Most Sellers will want you to place a significant amount of money into a trust account where it is held while you complete your conditions to the contract. It is wise of you to bring $5,000 to $10,000 CDN to put into a bank account here in your name so that you CAN put money on deposit with your purchase contract. The Seller’s will be much happier to work with you if you have made a financial commitment to the process. It is hard to predict how much of a deposit will be enough to satisfy the sellers until you actually select the home and enter the negotiation process. To help understand this process better you can read an article I wrote for Fresh Start magazine under the heading Purchasing Process.