Loss of brake pedal: This condition is usually a result of brake fluid leakage due to failure of a brake hose or a rusted metal brake line, a worn wheel cylinder or brake caliper, or a worn master cylinder. A simple once over of the system will reveal what's going on.
If you have questions about a specific purchase, it would be best to speak to an attorney who could inform you of your legal options. While there are laws that allow for a 3-day right to cancel certain purchases, these laws are very specific and do not apply in a majority of consumer purchases.
As one respondent said, if your agent had put a contingency in the contract for you to find a house to buy, and you had not, you could get out of the sale based on that contingency. However, absent that contingency you have no right to cancel unless the buyer breaches the contract.