No need for a trust if you and your wife are in the corporation, the corporation is allowed to own property including firearms.
A M16 will start at $10,000 and move on up as you want rare items.
LA also requires a state level permit in addition to the federal permit.
You will need to do federal paperwork each time the gun leaves your state of residence.
This dealer's website lists some dealers in your state, any one of them can answer your questions.
http://www.major-malfunction.com/maj_malf_5u_005.htm