Tell your uncle you would like to purchase the house on a land contract, so that you can get a few plants going to deal with you medical issues. Tell him the money you save from growing your own will help with the purchase of the house. If he doesn't like it, tell someone else and they will sell you a house.
What is the deal with the insurance not being covered? Seriously? Just on a rental, or any house with a grow? That sounds kinda hard to believe. This is a medical state. Insurance companies ask if you have a pitbull or a wood stove. They never asked me if I grew dope. I'm kinda lit, I may have misunderstood something.