It's not a perfect solution but you might consider doing what I did when I was in the military. I lived in the barracks where firearms were prohibited. The "official" rule was that if you were single and lived in the barracks, you were required to turn you POW's (Privately Owned Firearms) over to the Company armorer, who would then inventory them, noting the serial numbers, and store them in the arms room with the other weapons. If you wanted your weapons, it was up to you to contact the armorer and make arrangements to pick them up, signing them out and back in just as if they were one of your government issued weapons.

I'm pretty sure that in 10 years of active duty, I never knew anybody who did that. What most of us did was store them at the off-post home of a trusted friend, or, what I did was this:

When I got to a new duty station, the first place I'd stop - even before I signed into the post - was at a "U-Store-It" type place. I looked for one that was in a decent neighborhood and had good security (like gated access with alarms and a live-on-premises manager.) I would sign a contract for a small storage unit and into the unit would go my weapons and ammo. Then I would report into post and when inprocessing, they would ask "Do you have any privately owned firearms that you will be bringing onto the post?" I would truthfully answer "NO" because I always kept them off-post.

When I needed them, it was a simple matter of driving to my storage unit and picking them up, and bringing them back when I was done. At Fort Bragg, there was a gun club and shooting range on-post and I would bring my firearms onto post to shoot there. This was really not much of a risk because this was pre-9/11 and Bragg was an "open post" - you could just drive right on. Noawadays it would be riskier because Bragg (and every other military installation to my knowledge) is a closed post and there is always a possibility your vehicle will be searched (although not a large one.)

Anyway, getting back to my point - you could simply get a small storage locker, put your gun safe there and have access to your firearms when you needed them, without having to worry about the probationer. It's been a while since I've had a storage unit but you can probably find one for less than $100/month. Something to consider, anyway.