Here are a few things to be aware of especially since you are going after 50k properties in unfamiliar markets:- A roof replacement usually costs between 8k-12k range whether the house is worth 50k or 850k...that can be 20%+ of the properties value. 

Let me know what you do religiously that is worth the extra cost and what to avoid. 

Eric, the usual advice given to n00bs is that wholesaling is the path to follow.

Is this the same process for a duplex or quadplex or are there extra stipulations? 

I'd usually rather have a C house in an A neighborhood than an A house in a C neighborhood.What grade neighborhood are each of these properties in?

I would agree with the other Derek here that high leverage especially on your primary could have some extra layers of risk. 

Prepayment penalties- usually 1-5 year terms.

Since my parameters are quite specific ( NOT, hey I’m looking for a good deal, LOL) the responses rate while low is usually of fairly high quality.  

During your due dilligence period - I would pay for a home inspection like usual and have a mold expert come out and have the mold tested first. 

Hi Jack, I’ve currently got 25 units and it takes me about 4 hours per month to manage the banking/rent aspect of them, usually less than 2 hours per month to deal with the tenant issues and because I take it seriously and live close enough to all my properties to be able to visit them frequently I spend about 2 hours per week visiting each of them once (unless there’s a problem at one or more of them which isn’t often) for a total of 8 hours a month.