Some landlords try to get around the laws prohibiting discrimination against families by setting unreasonably low occupancy limits, such as only two people for a two-bedroom unit.

The contractor does not want to discount the price based on quality of the work, or unreasonably long time he's taking to complete this project; despite him knowing he cost me a lot of $$$ in lost rent.

Who knows how many people have keys to that door and yes it seems completely unreasonable for you and the tenant to not have a key to enter through the front door.  2. 

Or is it if it's something that we can argue was caused by unreasonable use? 

On the rare occasion, they really want to sell but have either no idea what the house is worth or an unreasonable expected value. 

You may have better luck asking for a 20% or so carry-back from the sellers, that's not uncommon or unreasonable in the commercial world. 

Such consent shall not be unreasonably withheld.

Am I being unreasonable in expecting those kinds of returns in that area, or is my offer to high?  

(B) If the landlord makes an entry in violation of division (A)(8) of this section, makes a lawful entry in an unreasonable manner, or makes repeated demands for entry otherwise lawful that have the effect of harassing the tenant, the tenant may recover actual damages resulting from the entry or demands, obtain injunctive relief to prevent the recurrence of the conduct, and obtain a judgment for reasonable attorney's fees, or may terminate the rental agreement.

I'd be concerned a judge would consider that unreasonable on anything less than a couple of grand per month rent.