Interested in getting some extra income with converting the extra space in the basement into a rentable unit.Basements in a one-family home can be lawfully rented only if the following conditions are met:Compliance with the Housing Maintenance Code for minimum room size.There is a minimum ceiling height of 7 ft.The walls, as high as ground level, must be damp- and water-proofed if HPD determines that subsoil conditions on the lot require it.The basement is occupied by one family and does not include boarders.Every room must have at least one window.The bottom of any yard or other required open space cannot be higher than six inches below the window sill of any required window in the room.

Most investors let the tenants pay down the mortgage and use extra money for their down payment on their next rental.  

-A water heater issue resulted in repeated mismanagement—confusing unit assignments—leading to extra costs to fix the same issue 3 times and on each occasion "more fixes" needed to the water heaters that I plumber said was needed.

I’d plan for extra amenities like special decor or concierge services. 

Some of this may have been grandfathered in, but now need updating.I would pay the extra say $50,000 to have an Engineer firm go over.

I've tried the lower 6-7% PMs and usually you'll either pay mark ups on repairs (what you've noted) or pay extra fees (i.e. labor hours, extra calls) that you may or may not notice. 

Early on in my career, I saw a close frend do something similar.. she borrowed from her circle to finance a rural fixer-upper, then paid them back once she refinanced after the rehab.I’m guessing that massive yard plus the barn is already a big selling point for your tenant, especially with a family that wants a little extra room for animals.

Requiring occupant to have renters insurance is another possibility for extra protection.

Possibly using mortgage/home equity loan on one unit we own to buy an extra one.3.

The only extra pay for guests is the surf-rider.