Listing Agent Dishonest About Current Rent

[JW Terry]

I'm currently buying a partially occupied duplex. The listing agent prior to me making an offer informed my agent that the occupied side rents for $700 per month. I crunched the numbers and eventually put in a full price offer based on the value of the home and the current rent. Everything was going smoothly until we saw the lease and it stated that the current rent was actually $100 less than what I was originally told. The lease was 8 years old so I assumed that the rent must have been raised as some point during that timeframe. So I request, via my agent, further proof that the rent is in fact $700. My agent responded, including a direct quote from the listing agent, with something along the lines of... 

I reply to my agent the following: 

He still hasn't responded and this was sent several days ago. To make matters worse, I promised the 70+ yr old widow tenant that she would not be forced to move once I took over the property (Awesome tenants who takes really good care of the unit). But not so awesome at $600. 

Is this a legal issue, if yes, do I have any recourse? Or have you ever experienced anything like this and what was the outcome. Thanks in advance!