But even beyond the math side, the hard part that cannot really be taught in a book, is what are your assumptions and are they realistic.  

By the time you get to 2/3rd of the way you end up just gutting and changing the entire layout anyways, so you might as well start with that end in mind and work from that assumption.

What assumptions were made?

@Ryan Dandrea, Hi I don't have much info to go on about you so I am going to make a few assumptions, in order to give you some advice.  

If I go with an Assumption, I would get a small down payment, maybe walk away with 5k in my pocket after the tax-man is done with me.

If you underwrite higher risk properties with all the same assumptions as higher end properties, they will also look like winners, but you will be working harder for every dollar here.  

Safe assumption that they would change once the deal is done. 2-Are the Dr's office/Apartments rented at market rate?

I didn't want to record it prior because I had no proof he wouldn't pay, and delaying settlement on assumption could have back fired.

I realize interest rate and other loan terms play into this, so I will preface it with using the same assumptions you did in my scenario.You stated a 60% LTV can open you to waiving many things, can you expand a little on that comment?

If you don't specifically address utility charges, just operate on the assumption they are due along with rent and late fees are applied on the same schedule.My lease says that all payments are applied to non-rent charges first (utilities, repairs, etc.) and oldest first.