@Douglas KrofcheckIf you have four separate units and wanted to install a central vacuum in each, it is possible each would need to be plumbed separately {for fire code reasons} - either back to a common mechanical room or within each unit - requiring a separate canister/motor to be installed for each.While a central vacuum would be a nice perk, I doubt it would be cost effective - it would likely be cheaper to finish all the units with hard flooring (no carpets) and buy a $50 Bissell Power Force bagless vacuum for each unit.  

My effective return on my down payment ends up being about 18%.  

Investors who know how to turn a wrench and swing a hammer will make big money on distressed real estate because there will be no other way to cost effectively rehab it.

To alter a month to month rental agreement you need to give them a written notice, typically 30 days before it takes effect.

I realize this effectively reduces the sale price of the house significantly.

Since your mom will be loaning you the money, gift tax should not apply but as suggested by @Michael Le $14k of that money could be gifted tax free and not loaned effectively saving you interest on the $14k.  

Honestly, there are many faster, cheaper, and more effective ways to gain actual-useful-real-world experience.I'd be happy to answer any questions you might have about the Real Estate MBA program at UW-Madison.

And it would be even better if you could sell the 4 to the same buyer, to reduce cost and uncertainty.But, in effect, your Replacement Property for each of the 4 Relinquished Properties would be a  1/4 interest in the new property.Hope this helps.Michael Lantrip

closed on a quadruplex property with 3 tenants in Athens,GA.Need a property management company who provide great service and cost effective management rate.Any recommendations 

This implies if you are doing forced appreciation, actively leveraging, performing profitable flips, etc then you can make significant money because you in effect have made RE a business.