Do you mean something like this?
CREATE TABLE locations
(
id INT NOT NULL,
country VARCHAR(64),
state VARCHAR(64),
street_address VARCHAR(64),
PRIMARY KEY(ID)
);
CREATE TABLE tours
(
id INT NOT NULL,
start_location INT NOT NULL,
end_location INT NOT NULL,
description VARCHAR(255),
cost DECIMAL(19,2),
date DATE,
PRIMARY KEY(ID),
FOREIGN KEY (start_location) REFERENCES locations (id),
FOREIGN KEY (end_location) REFERENCES locations (id)
);
Here is SQLFiddle demo