Now, the downsides are wear and tear (solution: parents to co-sign) and seasonality (solution: higher rents saved for those down times). 

-Finally if you can't find or afford the right property with a house on it already as above, the best rural new construction opportunities/deals are often land with a tear down mobile on it.

I would say that it would be normal wear & tear so you would be responsible for it. 

Get this out of General Landlording and into Creative Financing so we can tear it up! 

Winner winner chicken dinner....And then the young, never home, "no wear and tear" professionals come knocking!

Turned out my timing was perfect.The city demanded that I tear down the illegal unit wall to wall, and if I wanted something built, I had to start all over from scratch, with plans.

Most cities cap the number of people per bedroom at 2 so you are ok there but I think that many people are going to put a lot of wear & tear on the property. 

I would say " you have been good tenants" and i would take $600 to not move forward legally.I will draw up a small  dicument stating that i am happy with our new written agreement.If they have stayed there less that a year i would ask for more like $900.Take lots of pictures of any damage, wear and tear that is beyond normal wear and tear.Is their deposit, one months rent?

My area it $6  sf to tear out and install. 1200 sf*$6 sf = $7200/10 years life span/12 months in a year= $60 per month for 1 item.

Wear and tear is a fairly subjective term, so I would not assume you are getting a tenant to pay for much of anything at turnover.