I currently have several cards that combine to offer me roughly $3000 worth of free travel every single year that I can either use immediately, or stockpile it for my big world tour once I retire.  

If those lots are not counted in your Certificate of Zoning, you could appeal that they are wrong on the count (but you'll need a municipal lawyer to represent you) or you could go buy a $500 travel trailer and put that on the lot and see if you can get a city approval for electric hook-up (and if not, you're back to the attorney again).

My four units in the area are each 2 beds and rent for $700, $900, $1,000 and my sister lives in the 4th.

I would think that the tax's on the additional income would make it a wash.In addition you might (I'm not 100% sure) lose the 250K tax free deduction when you sell your primary residence, as it could be argued that it is ... well, a rental property and not your primary residence.When you have multiple properties and travel between them, it makes sense, not so sure on a single residence or everyone would be doing it and it would be all over the news, internet.

I am looking to build my portfolio enough so my wife and I can travel and have more family time with our son and soon (october) daughter.

@Patrick Daniel  we got the assumption part cleared up, but the brother and sister who own the property are in disagreement about a lien...going to be delayed over drama...but we will end up getting there. 

I lost my sister to drug addiction and I have struggled for a decade, since i was in my teens.

Willing to travel, move around and be in multiple markets.

I think putting your own eyes on it is definitely the right move, even though the travel is a hassle. 

Hello I’m looking for any suggestions on property inspectors in this area or that will travel to the area.