You must leverage to maximise returns.

If she were to willingly leave then you can do an addendum that they both must sign, to release her from the lease.

@Noah Weitzman As far as I understand it, if you have an active license and are not a broker, it must be hung under a sponsoring broker.

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Others have added an additional fee to tenant bill.Any change in rent (including adding utility costs) must be in writing usually with 60 notice.  

Since a vacancy is normally expected every 2 or 3 years max, does it mean that every 2 or 3 year, I must expect to pretty much make $0 annual profit?

I visited the link.

Must include:- obtaining all licenses and permits- tear down of existing structure(s)- complete build including finishes

Landlords must be very hands on to insure issues are reported early and that the tenant is respecting all community regulations.

I received 250 dollars off closing costs once by opening a checking account and went a head and used that account to hold rent deposits from that purchase.I once read a story off BP were a guy was told he MUST open a checking account to close a mortgage by a community bank.