Buying a property with questionable (no) access?

[Chris Krinslow]

I was inquiring about a property and the listing agent told me of another one she has for sale that's currently off-market. It's in a very good area of the city (Miami) and I'm confident it can generate a solid return based on the asking price, however there's just one catch (There always is!) -

The property is located behind another property. There are basically two homes (One in front of the other) on a rectangular shaped piece of land. They are on two separate folio's, owned by two different families, and each pay separate property taxes. 

So you have the road, and then a home with a drive-way. And behind that one is the home for sale. As of right now it looks like there is a "side driveway" leading to the back home. But I think that technically the "side driveway" is owned by the owner of the first home as it passed through their land. 

I'm wondering if this could present problems if say the owner of the "front house" is not friendly towards the new owner (potentially myself) or if the front house is sold at some point and again the new owners want to cut off access.

I wonder if they can legally cut off access or would they be required by law to provide access?

Too bad I'm not wealthy enough to offer helicopter service to tenants :P

Any help, advice or experience with such a situation would be appreciated. I have a lawyer, but this is not the type of question he specializes in. Working to find someone who can but figured I would ask here in the meanwhile.