I would look for a single family home that has the ability to be set up like a duplex - large bedroom with seperate outside entrance that you could convert to a studio with a small kitchenette..   

The Curb Appeal is Breathtaking and the home features a beautiful upgraded Tile Entrance.

Ie second kitchens, laundry, entrances, etc.

LL efficiently uses the flex space offering bonus rm, 2 BD, office nook, wet bar, full BA & separate entrance.

@Tina Lee good suggestion by @Nathan G. if you are DIY and have less than 20-30 or so doors.Unfortunately, the system he suggests gets cumbersome to manage at a certain scale.We've been using locksmiths for ages and here is how they do a master system:MASTER KEY- can have as many SFR doors you want under the master-MUTLI-FAMILY: can then add another layer of submasters, so you have a key that only opens every door in the building---Great for apartment type buildings where tenants often have a key for building entrance and another for unit entrance.

Lower w/ separate entrance plus 2nd brand new kitchen, dining and living.

Separate entrances/garages from the front.The bonus here is if I could also book the studio on occasion and when both book concurrently, I would travel and stay elsewhere. 

Gravel driveway, steep steps in the front, would have to roll through uneven clumpy grass to get to the back entrance. which still has a few steps. 

This may be an inlaw suite, a master bedroom with a back entrance that you can airbnb or a basement apartment.

Take a close look at separate sunroom entrances which can act as a second front door for your tenants.