The only way this could have an asymptote, either horizontal, vertical, or oblique is if it is a rational function, proper or improper. This function is linear:
y=3x-1 is what it simplifies to and it is a straight line through the y axis at -1 and has a positive slope of 3. There are no asymptotes here. But the y intercept, like I stated, is (0, -1)