We'll pop in a glass roller door to the back and create a zen garden and roof deck (which has killer views).  

Very economical when you get over 25ft tall.  

Most garages are not tall enough to allow a van with a ladder rack.

The 2' tall grass was an invitation to code enforcement.  

Start small grow tall.

and If not, seriously look with a magnifying glass as the project may be undercapitalized.

Getting permits to build tall buildings in Boston has been a painful process up until a few years ago.

As far as other maintenance expenses, as a landlord you're typically expected to fix whatever breaks on the property (e.g. sliding glass doors, screens, ceiling fans, light switches, faucets, leaky plumbing, garbage disposal rusts out, leaky toilet, garage door doesn't open, electrical issues, etc.)

In all honesty, that's a tall order with the exception of some strategic hard money lending or completing a couple solid flips per year, but that is active income.

Not just a few appliances, but a full kitchen with plates and glasses.