In a nutshell, the answer is: YOU BET! Currently I work from home, so more than likely, it's easier and much less expensive to just eat from home. On occasion (for biz meetings), I will eat an outside lunch or do an even less expensive meeting (in a good coffee type place).
When I wasn't working from home, I STILL brown bagged it mainly. This is such a money saver, and it felt good to put that savings literally in my "stash cash coffee-can".
Regarding ideas-leftovers make a great next day lunch. The trick is how they are packed. Invest in good microwavable food storage containers. They end up paying for themselves in savings.
Pre-pack leftover salads.
In the summer, I used to freeze a container of yogurt and take it frozen to work. By lunchtime, I had a nice, cool treat for lunch
Pack some easy to eat portable fruit, like an apple or bananna.
Avoid the messier ones if possible.
Hope this helps!