At the very least, disclosure should be made and acknowledged by the seller that B has reduced the effective purchase price below market value as set by the ultimate purchase price by the C buyer.

However, the reserves do not necessarily have to all be in cash - short term debt instruments or my favorite, a diversified Currency fund to reduce exposure to the dollar.

Further, by filing suit against these two, you may reduce the impact of the suits from your buyer and the agent.

But if you have each apartment complex in a separate LLC, then you reduce the likelihood of liability arising from one apartment complex exposing the other one to risk.

Lines are very hard to obtain for real estate investors right now AND they are subject to waxing and waning if the bank wants to increase or reduce risk.

If they are good people, stress free, boring, and take care of the property then I might reduce the rent a little to retain them.  

Each have 2 and 3 bedroom mix, near universities, C+ (ish) type properties competing against large scale, A+ type properties, reduced enrollment, possible saturation, etc.  

Reduced price to $595 per unit but still no tenants.

Maryland had a ground breaking law in the 90s to reduce lead poisoning and to protect landlords from lead paint lawsuits.

Doing so will ultimately reduce your potential problems, costs, turn around time, etc., with this and future tenants.