As mentioned before, it's definitely worthy to store your savings so that you are not easily able to access them.

I am debating whether to rent out the current unit I am living in (that has access to the backyard and pool) or sell the property and reinvest the gains into other projects.

A big thing that helped me was becoming an agent focused on investment property so my access to deals opened up as well as my earnings.

People can get frustrated or annoyed if you are constantly calling them. 

Do you have legal rights to access the property by crossing land owned by others?

I'm looking for opinions / guidance on whether or not this is possible - from a city regulations stand point:The second floor of a 2 family has an attic space with stair access from the 2nd floor apartment.

Make sure you check out all that this site has to offer.If you haven’t been to it already, you might want to check out the BP blog: https://www.biggerpockets.com/blog/There are a few self-contained guides that you can access here: https://www.biggerpockets.com/guides

You can install Nest thermostat and lock tenants from accessing, but they will still complain. 

Was not too hard to keep accurate books and my accountant had access to access, review, ask questions, etc.  

If it is not clearly stated that they are indeed assigned a parking spot, I don't know if they technically have access to it.