Cooking and Fishing go together perfectly, however the sushi market is really rough. A lot of fishermen and high level cooks dominate the market and you will get undercut. Most of the time, too, you will more make more money selling the fish you fish up to the AH or NPC (like soles).
Do not let that steer you away from Cooking. Personally, I love cooking. But it is true that the margin is not great. However there are a lot of positives:
Fishing and cooking go well together.
Cooking is a very cheap investment.
There are a lot of recipes that gain profit.
You can save money on your favorite food.
You can sell directly to people who have a certain niche for food (say, a BST in your LS who wants zeta cookies).
A lot of recipes can be made from NPC items (melon pies).
So, if I were you, I would take the 1.5M and either invest it into Cooking (but for the love of all that is holy, do not PL (if you must then do it)), or just taking fishing to 100. Fishing alone is a huge money maker.
Good luck to you :D.