Not sure exactly what's going on here with these air leaks, but can I just tape over these spots with foil HVAC tape? 

There is also the Dover air base there so I would research/ask questions here on BP about military housing.

Furthermore, we have also started using our home as an Air BNB rental and have found it to be great way to make passive income.  

the higher the class of property the easier MLS becomes.Just saying there are alternatives  you just need a good broker... who likes to work with investors.I referred a BP client to my broker in Charleston SC who then bought a 800k duplex.. that she got approved for air bnb for example and its now making her 5k a month Net after expenses and sometime more..  

@Mindy Jensen Air France can get you to Hawaii for 30k miles. 

I had to get drywall compound on all seams-Closet bi-fold doors were off their hangers -Front door needed some more weatherstripping to seal out cold air.  

I live in the north east maybe it is because it is cooler here, but on the big multi family units here they use a direct vent natural gas fired water heater and they run a heat loop off the tank for a hydro air handler.

I mean if we are just picking random companies out of thin air....

In fact  I don't know the credit history of any of my tenants - never checked it.Yes I check stuff, yes I have grounds for rejecting applicants, no the state of their credit isn't one of them, yes I know some people here will get apoplectic about that, no it doesn't make any sense to do that for the demographic that are going to apply for a rental in the hood.So with that out of the way and it is relevant context, I am going to post about conversation had with one of my tenants last week.Me: Hi it's starting to get warm and I noticed last year the house seemed rather hot in the summer are you alright for air conditioning.Tenant: We ok Mr O, we got some air conditioners last year.Me: Really, you bought portables.Tenant: No we bought some had someone install them in the windows.Me: You should have told me you needed that I would have got it for you.Tenant: That's ok Mr O.Me: Do you have the receipts so that I can reimburse you.Tenant: You don't need to do that Mr O we are ok. 

You don't have to say you want to come over and check the air filter or the smoke detector batteries or whatever to keep an eye on the place.