That's because the combustion byproducts are in a liquid form, so they need to be drained out of your home in a similar way the condensation from an air conditioner is drained outside.At least, that's my understanding of it.

Some years the yields really are that good, some years they are closer to zero (like when a roof and air conditioners need to be replaced - these things happen).Also, you mentioned increasing rent - having a steady tenant who actually pays their rent is much more valuable than pushing someone out and dealing with a couple months of vacancy for an extra $50/months in my experience.

I also had an air conditioner fail on move-in day in 100 degree heat.

My ‘highlights’ have been Hoa ‘weed notices’ or Air conditioner outages.  

Current residents have complained about high electric bill d/t window air conditioners to cool unit during summer d/t broken heat pump. 

But honestly, I just don't find their prices to be any better than the Big 3 wholesalers (costco, sam's, bj's). and also, their site UI is pretty horrendous to use - i find it much easier to search, sort and find items on costco, sams & bjs web sites than hdsupplysolutions.com.For regularly restocked supplies (TP, paper towels, shampoo, conditioner, soap, etc), does anyone know of anywhere cheaper to buy than the big 3 wholesalers' web sites?

Then you have to account for your time spent answering inquiries, booking guests, coordinating cleaners, telling people for the 27th time how to operate the remote control or air conditioner, etc.When you make a complete comparison, the AirBnB option may not produce a much better return and it can be a lot more work.

Things like coffee, tea, bottled water (our tap water is really hard and tastes gross), as well as items like toilet paper, shampoo, conditioner, hand soap, dish soap, etc. 

They are finally putting air conditioners in the two upstairs apartments, and are gutting the two downstairs and making it one big apartment, putting new carpet isn't one of their priorities and they are cheap, so I contacted my landlord and asked if I could replace the carpet, I took the measurements of the apartment and roughly it could cost anywhere from $350-500. 

Let the tenants provide window air conditioners and their own washer/dryer.