The shorter amortization will only decrease your interest payments.I would just be mindful about generating expenses just to pay less tax. 

Both of us are interested in using the rental from time to time since we enjoy the area, but I think that will decrease once we start using it. 

Currently I'm renting the same building for $505.06 due to the roof is leaking, it is currently involved in a lawsuit with the roofer as he did such a bad job that it caused me to take a $700 decrease in rent for now.I have a deal that has presented itself to me that I can obtain a 3br 2 ba, 2 story house with a tenant that has been in it for 4 years, rent is paying $750 a month and a purchase price of $75,000.00.My question is should I look at getting financing to get the commercial building roof fixed so that rent can come back up to $1,200.00 or try to get financing for the residential house with that tenant.My initial thought is to get financing to purchase the residential house and wait for the lawsuit to clear before fixing that up.

We buy 'value add' properties where we see an opportunity to raise income and decrease expenses.

Decreasing crime indexLike I said there are a bunch of other criteria you can and should look at depending on your strategy.

But my plan was to move into a duplex, use the decreased mortgage, from renting out the other side, as an opportunity to catapult into real estate investing. 

(Currently we pay $1050/mo in rent, this would decrease our overall payments to roughly $600 while generating some cash flow and building equity.)2.

Do some due diligence to better understand if their credit scores are increasing or decreasing. 

The bank can freeze or decrease the line if ever needed, e.g., this occurred during the financial crisis. 

They have broken the lease by moving in the mom, they leave the place unlocked, they leave windows open and you pay for heating and you already gave them a decreased rent.If rent is currently $2150-what do similar units go for now in your area?