Apartment troubles

I have an apartment that I rent out. I've had the same tenant for over a year, and he is paying about the same amount that my tenants have paid over the past 2.5 years. But he may be leaving soon, and I've quickly discovered that in today's economy, I will have to take about a 25% cut in rent. Ad on top of that, that my co-op just instituted a 7% charge for any rentals. Also, my monthly maintenance charges have increased 3%, and last year we had to pay over $2,000 in special assessments to cover the then ridiculously high fuel and utility costs to run the building.

Complicating the problem is that the next-door neighbors have made an very official noise complaint against my very UN-official tenant. So I tried to soothe that over today, and it wasn't easy. My neighbor is a curmudgeonly 60-something doctor, who spent 10 minutes trying to convince me that he wasn't some curmudgeonly 60-something. He tells me that my "friends" (the unofficial tenant) are too noisy when he's trying to sleep at night. I am very sensitive to my neighbors noise concerns, I really am. Partly because I'm a considerate bloke, but also partly because if he makes a stink about it, then I get on the radar of the building management and then questions come up about who exactly is living in the apartment. So I had a long heart-to-heart with my tenant who tells me a very different story. He makes it seem as though the neighbor is being intolerant of any noise at all, even simple conversation, late at night. I tend to believe my tenant, and I think the neighbor is making a big issue of very little, and yet this has the potential to cause me big problems. In fact, he may already have. And so, I may have to make my next tenant "official" which means paying about $900 in applications fees and move-in deposits in addition to the 7%. At some point, (and I'm quickly reaching that point) as I reduce the rent I charge and my expenses to rent increase, it will make no sense to have a tenant, and I will have to move back in myself.