The only thing I can say is:
The minimum value should be larger than the radius of the earth.
The maximum depend on how fast (\vec{v} and direction)and where you set it.

It is a easy problem only if it is a circular motion.
Gravitation force provide the necessary force \frac{GMm}{r^2}=m\frac{v^2}{r}
So  you can set v=\sqrt{\frac{GM}{r}}

It would become a very difficult problem if it is not circular motion.
Draw the effective potential might help(like the potential in the [url=http://www.phy.ntnu.edu.tw/ntnujava/index.php?topic=9.0]kepler motion [/url]page.

Remember: It is the physics law combine with initial values which decide the trajectory.