Not only do I rent from her but I am getting a below market rate on the property I am in. 

What do you think I can do with below wood burning fireplace.

These would easily rent at $750 per month which is slightly below market rent.  

Just make sure to try and acquire the property at below market value -- that's where the bulk of your money will be made.

I attached an example down below

However, if it's difficult to get a full accounting of the owner/landlord's assets then my guess is that the chances of a lawsuit are generally expected to be lower.  

If you do this, your profits will be lower (you have to pay the loan costs), but you may find that your percentage returns are even higher.- There are people who prefer to invest in areas where houses resell for $100K; there are others who prefer to invest in areas where houses sell for $1M+.

My simple advice would be to buy good cash flowing rentals below market value, manage them yourself, and keep re-investing the profits as future down payments on your next rental.  

So the goal is to the keep the unit rents cheap way below market so they never leave.

That's 75k below asking price.If he has a renter in there already covering the mortage he has no incentive to sell.However it's possible you could maybe see if you can do owner financing or take over his existing mortgage.