import string
import random


def get_random_string(length: int) -> str:
    """
    Returns a random string starting with a lower-case letter.
    Later parts can contain numbers, lower- and uppercase letters.

    Note: Random Seed should be set somewhere in the program!
    :param length: How long the required string must be. length > 0 required.
    :return: a randomly created string
    :raises: ValueError for zero and negative length
    """
    if length < 1:
        raise ValueError("Random Strings must have length 1 minimum.")
    # choose from all lowercase letter
    letters = string.ascii_letters + string.digits
    first_letter = random.choice(string.ascii_lowercase)
    result_str = ''.join(random.choice(letters) for i in range(length - 1))
    return first_letter + result_str