If you are offering your product for sale and not for free, then you will most likely make money from it. If what you are asking is how to maximize the income and prevent piracy, then that is a more specific question.
The key to making money with software is to make the purchase route less painful then the piracy route. Usually the biggest hurdle to purchasing software is the price tag (but not always, some people just will never buy software and always pirate, but you can't do anything about that). And the biggest hurdle to piracy is some sort of DRM scheme, which is actually the second largest hurdle to purchasing software. Often times DRM only annoys the legitimate purchases, while the pirated version has all the DRM removed with less effort then you spend to put it in. Thanks to the wonder of electronic duplication, once the DRM is removed, then everyone can have a DRM free copy.
So you want a solution that only annoys illegitimate usage, but not legitimate purchases. This is much harder to do then expected.
Depending on the price tag for your software you might consider deploying it on a keyed USB drive (i.e. Dongle or USB stick with some special key). Then it is portable, but only on the hardware you provide. The user never has to worry about a secondary authentication scheme, and the DRM only becomes an issue when the hardware (which is harder to duplicate) is changed.
You say that it is only for a LAN environment, which doesn't necessarily mean that the computers will have internet access (and if they do, they probably have a proxy requirement) which means "phoning home" will be problematic. If you want the product to only be used on a specific LAN then you might require a license server to be installed on the LAN. Then the software could always check with the license server to make sure it is authorized. That won't work if you want it to run on multiple LAN's though.
Conversely if your price is low enough then most companies and people would rather buy the correct licenses and not risk the piracy. In actuality, depending on your clientele, most people will prefer legitimate licenses when they can, and DRM can actually discourage them from buying licenses.