I'd say something that would make it more attractive to a family would be school districts, these would drive up costs, but might not translate to much higher rent. 

I don't know what that means, but I'll translate it to, "Cuppa tea?"

Are you willing to help him alter his lifestyle to make better use of the money he has (very low probability of success) or teach him how increase his income (also very low probability of success)?

Thanks  I'm reading between the lines, but what I'm translating here is that the tenant is complaining, but you have no evidence that the tenant's concerns are valid.What I'd do is offer to let the tenant out of their lease. 

South of Boston we can get high efficiency FHW units installed for much less than the "new heating systems will sink you $10k and wipe you out" scare tactic excuse people use for not investing, not sure how that cost translates to NY.  

If a tenant chooses not to use the vent, that's on them.So, provide a quieter fan if you just don't want to deal with it (which would be my choice) or give a written warning to the tenants that disabling the fan is a violation of their lease agreement (I'm sure you have a clause about damaging the property or making alterations without permission), and they need to knock it off - and that any damage resulting from them disabling or not using the fan is their responsibility.And of course, you can always not renew their lease.

@Daniel Lehman, now that there's more information on the table, I think some people might alter their advice a bit.

My lease states (removed the parts not at all applicable):Deductions:(a) damages to the Property, excluding normal wear and tear, and all reasonable costs associated to repair the Property;(b) costs for which Tenant is responsible to clean, deodorize, exterminate, and maintain the Property;(f) unpaid pet charges;(q) cost to restore walls, flooring, landscaping or any alteration to the Property not approved in writing by Landlord; and(r) damages to the Property caused by smoking, including but not limited to stains, burns, odors, and removal of debris.Here's a photo of one of the door frames, for example.

You may even be able to demand they be altered (neutered or spayed).

This translates to a savings of around $7k for me on a typical deal.