I am surprised by the current on-market deals as supply seems to be very limited west of the 15 highway and in Henderson.

As long as the total availability of money supply is not reducing, then the price of homes will continue to rise.

However the more volume you have the more of an emphasis your job will have on a contractors schedule.Phoenix is definitely a landlord friendly state, both on a lawful level and a supply/demand level.

This indicates a back log of supply. 

In general you can't get to this goal by buying a retail property off the MLS because if you could, everyone would buy them (i.e. demand would be high, supply would not increase and prices would go up)  Banks in general will finance around 80% of the fair market value of the property, so you need to pay 80% for a property worth 100%. 

I do it all myself so I didnt have to pay much other than for supplies, but I'm still in the high $30,000's to do it.

Does it include supplies, tile, countertops, appliances? 

The problem is trying to use a percentage of a moving target to supply needed cash that is very specific. 

Some of the outside on/off shut off valves for the water supply were "frozen"The roof has some missing shingles from wind damage and missing rubber gaskets around piping that protrudes through the roof which allows water to get inside the attic.This is a question for anybody who wants to chime in.What other due diligence should I be conducting for an off-market seller financed 6 unit apartment building that comes with an adjacent vacant parcel? 

I would go with a hard money loan if the conventional path is: i) not fast enough to fund; ii) you're tapped out on a global LTV basis; iii) you need up to 100% of rehab costs to be covered, which I know isn't your case; and/or iv) you want a loan to be underwritten with the asset in mind and minimal emphasis placed on borrower FICO.