I do rely on a bird dog, my property manager, my roofer and my 1st ex wife's second cousin ( only kidding on the last one ) for viewing, drive byes, prowling, and an occasional break in.

@Omar Khan, great lifestyle but betting harder to do RE business. 

If you do re-sign this tenant with the $200 as part of the terms of the lease - this will be reflected as a loss of $200 per income each month when fully repaid on your books.

That said, retail buyers do rely on it to a certain extent. 

How do RE investors keep track of their investment properties.

How often do RE deals fall through and result in litigation?

I want to do RE full time.

Exception:  you are an employee of the owner (typically builder/developer) and showing only their properties.That being said, I know of lots of people that are doing just what you propose, and are doing so knowingly or unknowingly breaking the DORE laws, at lest for NY and PA. 

I like to buy a property that is vacant, but if the old landlord doesn't want to kick the tenants out, and deliver to you vacant, not much you can do. RE

Mobile homes can be a great way to do RE.