Is there anything going on like mold, lead, asbestos, or the fact that it used to be a gas station in the 20's and still has concealed tanks?

@Joseph Dimaria Trusts are designed to conceal the identity of the beneficiary.  

My handyman stopped by a couple of times for repairs and gave me updates on what he saw; however, with me needing to notify the tenants before being able to enter the house the tenants were able to conceal what I suspected but couldn't find any hard core proof.

#1-I have done many double closings but prefer not to due to the extra costs and being in the chain of title if even for a minute, but it is a way to conceal your profit amounts from the owner who will think you screwed him when he bought from you , and a buyer who will think you screwed him.when he bought from you.#2-I like land trusts and LLC's to do the same concealing thing without the extra costs.

If you live in a state where the inspector is licensed, he could get in hot water for ethical violations and concealing a conflict of interest in his reply to you.Was it a full scope home inspection?

The Statutory Fraud Act does not always require you to prove the seller’s knowledge of a condition, so in many cases it is easier to recover under the Statutory Fraud Act than it would be to recover based on common law fraud.https://www.nolo.com/legal-encyclopedia/legal-remedies-if-home-seller-lies-conceals-defect-texas.html

If you're hard up for cash then spend $50 on a trail cam and conceal it well enough (perhaps behind some garbage) so it's not easily seen. 

I do conceal carry, but that does not mean I want to have to use that option...

All that said, boilers can be expensive to repair/replace, so when that time does inevitably come, I'll just have the tenants switch to the forced air furnaces and get rid of the boilers at that point.To your concerns about the ductwork in the basement, depending on the layout & size of the area, you could potentially conceal some of the ducts between the floor joists overhead.

The program was effective at concealing the source of funds and it was implemented to attract mortgage brokers looking to enhance their business.