mySQL Help? Can anyone help correct this code?

The error i am getting below

ERROR 1215 (HY000): Cannot add foreign key constraint

# # inventory-schema.sql file # DROP DATABASE IF EXISTS inventory; CREATE DATABASE inventory; USE inventory;

# # is used for comment in MySQL #DROP TABLE item_type; CREATE TABLE item_type ( name varchar(25), location varchar(25), upc int(11), weight int(11), sku int(11), item_price int(11), qty int(11), primary key (name), unique (item_price) );

#DROP TABLE owner; #CASCADE CONSTRAINTS; CREATE TABLE owner ( name varchar(25), birthday date, ossn integer, primary key (ossn) );

#DROP TABLE employee; #CASCADE CONSTRAINTS; CREATE TABLE employee ( name varchar(25) not null, salary integer, essn integer, postion varchar(25), owner varchar(25), o_ssn integer not null, manages_item varchar(25), primary key (essn), foreign key (o_ssn) references owner(ossn) on delete set null on update cascade );

#DROP TABLE transaction; #CASCADE CONSTRAINTS; CREATE TABLE transaction ( tid integer, qty integer, amount integer, item varchar(25), employee_name varchar(25) not null, primary key (tid), foreign key (employee_name) references employee(name) on delete set null on update cascade );

#DROP TABLE payment_method; #CASCADE CONSTRAINTS; CREATE TABLE payment_method ( type varchar(25), card integer not null, card_n integer not null, cash integer, check_1 integer, checkn integer not null, tid integer, primary key (type), unique key (tid) );

#DROP TABLE card_type; #CASCADE CONSTRAINTS; CREATE TABLE card_type ( name varchar(25), card_number integer not null, sec_code integer, exp_date integer, primary key (name)

);

#DROP TABLE check_type; #CASCADE CONSTRAINTS; CREATE TABLE check_type ( name varchar(25), check1 integer not null, tid integer, routing_number integer, bank_number integer, primary key (tid), foreign key (check1) references payment_method(checkn) on delete set null on update cascade );

#DROP TABLE cash; #CASCADE CONSTRAINTS; CREATE TABLE cash ( amount integer, tid integer, primary key (amount) );