I just needed to know a good company to call to get a ballpark on what a small, medium, and large remediation would cost.

My guess, some will, some won't at which time you can give the poor payers the 30 days notices (essentially giving them a probationary period with the month to month and new rules to see which tenants can handle the new format and which can't ). 

Detached one car garage, large basement for storage and laundry (also new).

With a large downpayment, it will be much easier for you to secure financing.  

Does he have a large investor base willing to dole out gold like that??

It would be a wonderful world if everyone could afford every safety device and had time to research them, but the truth is that sometimes you have to wait until time and money permit you to set up things for a large company. 

In a large city, people are cut throat and motivated, by greed.

It is a large piece of land that they are offering at an owner contract with 25% down.

Understand that this is large volume, so if you look at just one months mailing it may not fall in those stats, even though your 1/500 falls exactly at 0.2%.  

I have had to lower rents during the downturn to keep tenants as markets dropped, and I now make sure I raise rents at least every 2 years in rising markets as small incremental increases are a much better way to keep a long-term tenant than a large increase when your profits are eaten away by increased costs.