Assuming I'm looking at the same property on MLS, it's got potential.Have you factored in any rehab costs?  

age, location, size, and cost of replacement are all major factors for insurance, unfortuantely your purchase price doesn't matter too much!

Now I realized that I had given them a long free ride and  I must do a new lease factoring how large the family have increased.

@Ryan Agustin For conventional financing assets and income and DTI's are the important factor. 

You didn't say how long you think you'll own the home, that should be factored in.

What 'ugly' factor can you accept in exchange for the great price?  

Remember when looking at value you need to look at all the factors involved - including the neighbors.  

What kind of extra expenses does everyone take into account for the additional units, are there any economies of scale, how do your factors change?

I fully understand leveraging and the multitude of other factors that go into real estate investing and creating an ability to scale, but I also do not like the thought of emptying the back account to try and acquire a property.

You can use cash as a negotiating factor to get the price down along with coming up on your closing date.