I told him as a mild inconvenience I'll drop his rent to 500 (mistake number 1 as it was nothing in the contract about if/ when someone else moves in) He text me later saying he doesn't think 500 is sufficient as that is another person in the space, using hot water, in the living room, using W/D etc (which the living room I furnished and all of that I pay for).

Drop the price that's attractive to an investor.

If my insurance will drop me due to a certain breed then wouldn’t that be considered an unreasonable request? 

If your building survives, but all the surrounding ones collapse, demand to rent in your area will decrease, and rents will drop (for a while, not forever).If you're considering a three story tuck-under (that is, a building with parking stalls on the first floor and then 2 stories of living space above) and plan to hold it a while, do not buy without a plan to retrofit, which will cost a pretty penny.Single story ranch style home from the 1960s? 

Additionally, we have installed thermostats on the supply piping in the most vulnerable section of the basement which automatically turn-on the heat wrap if the temperature of the pipe drops below 1-2C.

If you change the terms to 8% for 100 months the payment drops to $302.13.PS I am not a lawyer and don't play one on TV so check your local laws on this one.

I sold cars for many years and made great money at it but last year sales dropped bad and I had just bought a house and had taken on new bills that I had to pay.

If well water drop the expense ratio below 50% maybe by alot.  

Do you think it will hold or drop a little?

The other photo shows an 8' counter top with drop down waterfall legs that are seamless.